Remove the always-true __INTRODUCED_IN() annotations.

The NDK no longer supports API levels earlier than 21.

This *doesn't* include <ctype.h> because I have a separate change
rewriting that (that's blocked on the upcoming libc++ update).

Test: treehugger
Change-Id: I53e915f27011dfc0513e0c78d8799377e183ceca
diff --git a/libc/include/sys/auxv.h b/libc/include/sys/auxv.h
index bf70dda..b664e2a 100644
--- a/libc/include/sys/auxv.h
+++ b/libc/include/sys/auxv.h
@@ -45,9 +45,7 @@
  *
  * Returns the corresponding value on success,
  * and returns 0 and sets `errno` to `ENOENT` on failure.
- *
- * Available since API level 18.
  */
-unsigned long int getauxval(unsigned long int __type) __INTRODUCED_IN(18);
+unsigned long int getauxval(unsigned long int __type);
 
 __END_DECLS
diff --git a/libc/include/sys/endian.h b/libc/include/sys/endian.h
index 9155b4c..1c7448c 100644
--- a/libc/include/sys/endian.h
+++ b/libc/include/sys/endian.h
@@ -49,10 +49,10 @@
 
 /* glibc compatibility. */
 __BEGIN_DECLS
-uint32_t htonl(uint32_t __x) __attribute_const__ __INTRODUCED_IN(21);
-uint16_t htons(uint16_t __x) __attribute_const__ __INTRODUCED_IN(21);
-uint32_t ntohl(uint32_t __x) __attribute_const__ __INTRODUCED_IN(21);
-uint16_t ntohs(uint16_t __x) __attribute_const__ __INTRODUCED_IN(21);
+uint32_t htonl(uint32_t __x) __attribute_const__;
+uint16_t htons(uint16_t __x) __attribute_const__;
+uint32_t ntohl(uint32_t __x) __attribute_const__;
+uint16_t ntohs(uint16_t __x) __attribute_const__;
 __END_DECLS
 
 #define htonl(x) __swap32(x)
diff --git a/libc/include/sys/epoll.h b/libc/include/sys/epoll.h
index 9e09408..2091b90 100644
--- a/libc/include/sys/epoll.h
+++ b/libc/include/sys/epoll.h
@@ -38,11 +38,11 @@
 __BEGIN_DECLS
 
 int epoll_create(int __size);
-int epoll_create1(int __flags) __INTRODUCED_IN(21);
+int epoll_create1(int __flags);
 
 int epoll_ctl(int __epoll_fd, int __op, int __fd, struct epoll_event* __BIONIC_COMPLICATED_NULLNESS __event);
 int epoll_wait(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms);
-int epoll_pwait(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms, const sigset_t* _Nullable __mask) __INTRODUCED_IN(21);
+int epoll_pwait(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms, const sigset_t* _Nullable __mask);
 int epoll_pwait64(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms, const sigset64_t* _Nullable __mask) __INTRODUCED_IN(28);
 
 __END_DECLS
diff --git a/libc/include/sys/fsuid.h b/libc/include/sys/fsuid.h
index c1c8ebb..273749f 100644
--- a/libc/include/sys/fsuid.h
+++ b/libc/include/sys/fsuid.h
@@ -43,19 +43,15 @@
  * filesystem checks.
  *
  * Returns the previous UID.
- *
- * Available since API level 21.
  */
-int setfsuid(uid_t __uid) __INTRODUCED_IN(21);
+int setfsuid(uid_t __uid);
 
 /**
  * [setfsgid(2)](http://man7.org/linux/man-pages/man2/setfsgid.2.html) sets the GID used for
  * filesystem checks.
  *
  * Returns the previous GID.
- *
- * Available since API level 21.
  */
-int setfsgid(gid_t __gid) __INTRODUCED_IN(21);
+int setfsgid(gid_t __gid);
 
 __END_DECLS
diff --git a/libc/include/sys/inotify.h b/libc/include/sys/inotify.h
index e834d07..f070857 100644
--- a/libc/include/sys/inotify.h
+++ b/libc/include/sys/inotify.h
@@ -41,7 +41,7 @@
 #define IN_NONBLOCK O_NONBLOCK
 
 int inotify_init(void);
-int inotify_init1(int __flags) __INTRODUCED_IN(21);
+int inotify_init1(int __flags);
 int inotify_add_watch(int __fd, const char* _Nonnull __path, uint32_t __mask);
 int inotify_rm_watch(int __fd, uint32_t __watch_descriptor);
 
diff --git a/libc/include/sys/mman.h b/libc/include/sys/mman.h
index cbe6a75..f32ae61 100644
--- a/libc/include/sys/mman.h
+++ b/libc/include/sys/mman.h
@@ -59,10 +59,8 @@
  * mmap64() is a variant of mmap() that takes a 64-bit offset even on LP32.
  *
  * See https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md
- *
- * Available since API level 21.
  */
-void* _Nonnull mmap64(void* _Nullable __addr, size_t __size, int __prot, int __flags, int __fd, off64_t __offset) __INTRODUCED_IN(21);
+void* _Nonnull mmap64(void* _Nullable __addr, size_t __size, int __prot, int __flags, int __fd, off64_t __offset);
 
 /**
  * [munmap(2)](http://man7.org/linux/man-pages/man2/munmap.2.html)
@@ -107,21 +105,17 @@
  * [mlockall(2)](http://man7.org/linux/man-pages/man2/mlockall.2.html)
  * locks pages (preventing swapping).
  *
- * Available since API level 17.
- *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int mlockall(int __flags) __INTRODUCED_IN(17);
+int mlockall(int __flags);
 
 /**
  * [munlockall(2)](http://man7.org/linux/man-pages/man2/munlockall.2.html)
  * unlocks pages (allowing swapping).
  *
- * Available since API level 17.
- *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int munlockall(void) __INTRODUCED_IN(17);
+int munlockall(void);
 
 /**
  * [mlock(2)](http://man7.org/linux/man-pages/man2/mlock.2.html)
diff --git a/libc/include/sys/resource.h b/libc/include/sys/resource.h
index 0b540de..6743343 100644
--- a/libc/include/sys/resource.h
+++ b/libc/include/sys/resource.h
@@ -46,8 +46,8 @@
 int getrlimit(int __resource, struct rlimit* _Nonnull __limit);
 int setrlimit(int __resource, const struct rlimit* _Nonnull __limit);
 
-int getrlimit64(int __resource, struct rlimit64* _Nonnull __limit) __INTRODUCED_IN(21);
-int setrlimit64(int __resource, const struct rlimit64* _Nonnull __limit) __INTRODUCED_IN(21);
+int getrlimit64(int __resource, struct rlimit64* _Nonnull __limit);
+int setrlimit64(int __resource, const struct rlimit64* _Nonnull __limit);
 
 int getpriority(int __which, id_t __who);
 int setpriority(int __which, id_t __who, int __priority);
@@ -55,7 +55,7 @@
 int getrusage(int __who, struct rusage* _Nonnull __usage);
 
 int prlimit(pid_t __pid, int __resource, const struct rlimit* _Nullable __new_limit, struct rlimit* _Nullable __old_limit) __INTRODUCED_IN_32(24) __INTRODUCED_IN_64(21);
-int prlimit64(pid_t __pid, int __resource, const struct rlimit64* _Nullable __new_limit, struct rlimit64* _Nullable __old_limit) __INTRODUCED_IN(21);
+int prlimit64(pid_t __pid, int __resource, const struct rlimit64* _Nullable __new_limit, struct rlimit64* _Nullable __old_limit);
 
 __END_DECLS
 
diff --git a/libc/include/sys/select.h b/libc/include/sys/select.h
index 8c6c2ff..84c2621 100644
--- a/libc/include/sys/select.h
+++ b/libc/include/sys/select.h
@@ -71,9 +71,9 @@
     } \
   } while (0)
 
-void __FD_CLR_chk(int, fd_set* _Nonnull , size_t) __INTRODUCED_IN(21);
-void __FD_SET_chk(int, fd_set* _Nonnull, size_t) __INTRODUCED_IN(21);
-int __FD_ISSET_chk(int, const fd_set* _Nonnull, size_t) __INTRODUCED_IN(21);
+void __FD_CLR_chk(int, fd_set* _Nonnull , size_t);
+void __FD_SET_chk(int, fd_set* _Nonnull, size_t);
+int __FD_ISSET_chk(int, const fd_set* _Nonnull, size_t);
 
 #define __FD_CLR(fd, set) (__FDS_BITS(fd_set*,set)[__FDELT(fd)] &= ~__FDMASK(fd))
 #define __FD_SET(fd, set) (__FDS_BITS(fd_set*,set)[__FDELT(fd)] |= __FDMASK(fd))
diff --git a/libc/include/sys/sendfile.h b/libc/include/sys/sendfile.h
index 4b00d5d..e1a34d2 100644
--- a/libc/include/sys/sendfile.h
+++ b/libc/include/sys/sendfile.h
@@ -40,15 +40,13 @@
 
 /* See https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md */
 #if defined(__USE_FILE_OFFSET64)
-ssize_t sendfile(int __out_fd, int __in_fd, off_t* _Nullable __offset, size_t __count) __RENAME(sendfile64) __INTRODUCED_IN(21);
+ssize_t sendfile(int __out_fd, int __in_fd, off_t* _Nullable __offset, size_t __count) __RENAME(sendfile64);
 #else
 /**
  * [sendfile(2)](http://man7.org/linux/man-pages/man2/sendfile.2.html) copies data directly
  * between two file descriptors.
  *
  * Returns the number of bytes copied on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 21.
  */
 ssize_t sendfile(int __out_fd, int __in_fd, off_t* _Nullable __offset, size_t __count);
 #endif
@@ -57,6 +55,6 @@
  * Like sendfile() but allows using a 64-bit offset
  * even from a 32-bit process without `__FILE_OFFSET_BITS=64`.
  */
-ssize_t sendfile64(int __out_fd, int __in_fd, off64_t* _Nullable __offset, size_t __count) __INTRODUCED_IN(21);
+ssize_t sendfile64(int __out_fd, int __in_fd, off64_t* _Nullable __offset, size_t __count);
 
 __END_DECLS
diff --git a/libc/include/sys/signalfd.h b/libc/include/sys/signalfd.h
index f669cc8..2be9bdc 100644
--- a/libc/include/sys/signalfd.h
+++ b/libc/include/sys/signalfd.h
@@ -45,10 +45,8 @@
  * file descriptor for reading signal events.
  *
  * Returns the file descriptor on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 18.
  */
-int signalfd(int __fd, const sigset_t* _Nonnull __mask, int __flags) __INTRODUCED_IN(18);
+int signalfd(int __fd, const sigset_t* _Nonnull __mask, int __flags);
 
 /**
  * Like signalfd() but allows setting a signal mask with RT signals even from a 32-bit process.
diff --git a/libc/include/sys/socket.h b/libc/include/sys/socket.h
index 821c483..22b88cb 100644
--- a/libc/include/sys/socket.h
+++ b/libc/include/sys/socket.h
@@ -120,7 +120,7 @@
    ? (struct cmsghdr*) (msg)->msg_control : (struct cmsghdr*) NULL)
 #define CMSG_OK(mhdr, cmsg) ((cmsg)->cmsg_len >= sizeof(struct cmsghdr) &&   (cmsg)->cmsg_len <= (unsigned long)   ((mhdr)->msg_controllen -   ((char*)(cmsg) - (char*)(mhdr)->msg_control)))
 
-struct cmsghdr* _Nullable __cmsg_nxthdr(struct msghdr* _Nonnull __msg, struct cmsghdr* _Nonnull __cmsg) __INTRODUCED_IN(21);
+struct cmsghdr* _Nullable __cmsg_nxthdr(struct msghdr* _Nonnull __msg, struct cmsghdr* _Nonnull __cmsg);
 
 #define SCM_RIGHTS 0x01
 #define SCM_CREDENTIALS 0x02
@@ -292,17 +292,16 @@
 #endif
 
 __socketcall int accept(int __fd, struct sockaddr* _Nullable __addr, socklen_t* _Nullable __addr_length);
-__socketcall int accept4(int __fd, struct sockaddr* _Nullable __addr, socklen_t* _Nullable __addr_length, int __flags) __INTRODUCED_IN(21);
+__socketcall int accept4(int __fd, struct sockaddr* _Nullable __addr, socklen_t* _Nullable __addr_length, int __flags);
 __socketcall int bind(int __fd, const struct sockaddr* _Nonnull __addr, socklen_t __addr_length);
 __socketcall int connect(int __fd, const struct sockaddr* _Nonnull __addr, socklen_t __addr_length);
 __socketcall int getpeername(int __fd, struct sockaddr* _Nonnull __addr, socklen_t* _Nonnull __addr_length);
 __socketcall int getsockname(int __fd, struct sockaddr* _Nonnull __addr, socklen_t* _Nonnull __addr_length);
 __socketcall int getsockopt(int __fd, int __level, int __option, void* _Nullable __value, socklen_t* _Nonnull __value_length);
 __socketcall int listen(int __fd, int __backlog);
-__socketcall int recvmmsg(int __fd, struct mmsghdr* _Nonnull __msgs, unsigned int __msg_count, int __flags, const struct timespec* _Nullable __timeout)
-  __INTRODUCED_IN(21);
+__socketcall int recvmmsg(int __fd, struct mmsghdr* _Nonnull __msgs, unsigned int __msg_count, int __flags, const struct timespec* _Nullable __timeout);
 __socketcall ssize_t recvmsg(int __fd, struct msghdr* _Nonnull __msg, int __flags);
-__socketcall int sendmmsg(int __fd, const struct mmsghdr* _Nonnull __msgs, unsigned int __msg_count, int __flags) __INTRODUCED_IN(21);
+__socketcall int sendmmsg(int __fd, const struct mmsghdr* _Nonnull __msgs, unsigned int __msg_count, int __flags);
 __socketcall ssize_t sendmsg(int __fd, const struct msghdr* _Nonnull __msg, int __flags);
 __socketcall int setsockopt(int __fd, int __level, int __option, const void* _Nullable __value, socklen_t __value_length);
 __socketcall int shutdown(int __fd, int __how);
diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index f773ff6..f916573 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -141,13 +141,13 @@
 int mkdir(const char* _Nonnull __path, mode_t __mode);
 
 int fstat(int __fd, struct stat* _Nonnull __buf);
-int fstat64(int __fd, struct stat64* _Nonnull __buf) __INTRODUCED_IN(21);
+int fstat64(int __fd, struct stat64* _Nonnull __buf);
 int fstatat(int __dir_fd, const char* _Nonnull __path, struct stat* _Nonnull __buf, int __flags);
-int fstatat64(int __dir_fd, const char* _Nonnull __path, struct stat64* _Nonnull __buf, int __flags) __INTRODUCED_IN(21);
+int fstatat64(int __dir_fd, const char* _Nonnull __path, struct stat64* _Nonnull __buf, int __flags);
 int lstat(const char* _Nonnull __path, struct stat* _Nonnull __buf);
-int lstat64(const char* _Nonnull __path, struct stat64* _Nonnull __buf) __INTRODUCED_IN(21);
+int lstat64(const char* _Nonnull __path, struct stat64* _Nonnull __buf);
 int stat(const char* _Nonnull __path, struct stat* _Nonnull __buf);
-int stat64(const char* _Nonnull __path, struct stat64* _Nonnull __buf) __INTRODUCED_IN(21);
+int stat64(const char* _Nonnull __path, struct stat64* _Nonnull __buf);
 
 int mknod(const char* _Nonnull __path, mode_t __mode, dev_t __dev);
 mode_t umask(mode_t __mask);
@@ -156,12 +156,12 @@
 #include <bits/fortify/stat.h>
 #endif
 
-int mkfifo(const char* _Nonnull __path, mode_t __mode) __INTRODUCED_IN(21);
+int mkfifo(const char* _Nonnull __path, mode_t __mode);
 int mkfifoat(int __dir_fd, const char* _Nonnull __path, mode_t __mode) __INTRODUCED_IN(23);
 
 int fchmodat(int __dir_fd, const char* _Nonnull __path, mode_t __mode, int __flags);
 int mkdirat(int __dir_fd, const char* _Nonnull __path, mode_t __mode);
-int mknodat(int __dir_fd, const char* _Nonnull __path, mode_t __mode, dev_t __dev) __INTRODUCED_IN(21);
+int mknodat(int __dir_fd, const char* _Nonnull __path, mode_t __mode, dev_t __dev);
 
 /**
  * Used in the tv_nsec field of an argument to utimensat()/futimens()
@@ -200,10 +200,8 @@
  * See also UTIME_NOW and UTIME_OMIT.
  *
  * Returns 0 on success and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int futimens(int __fd, const struct timespec __times[_Nullable 2]) __INTRODUCED_IN(19);
+int futimens(int __fd, const struct timespec __times[_Nullable 2]);
 
 #if defined(__USE_GNU)
 /**
diff --git a/libc/include/sys/statvfs.h b/libc/include/sys/statvfs.h
index d81f836..46fbea5 100644
--- a/libc/include/sys/statvfs.h
+++ b/libc/include/sys/statvfs.h
@@ -93,25 +93,21 @@
  * queries filesystem statistics for the given path.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int statvfs(const char* _Nonnull __path, struct statvfs* _Nonnull __buf) __INTRODUCED_IN(19);
+int statvfs(const char* _Nonnull __path, struct statvfs* _Nonnull __buf);
 
 /**
  * [fstatvfs(3)](http://man7.org/linux/man-pages/man3/fstatvfs.3.html)
  * queries filesystem statistics for the given file descriptor.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int fstatvfs(int __fd, struct statvfs* _Nonnull __buf) __INTRODUCED_IN(19);
+int fstatvfs(int __fd, struct statvfs* _Nonnull __buf);
 
 /** Equivalent to statvfs() . */
-int statvfs64(const char* _Nonnull __path, struct statvfs64* _Nonnull __buf) __INTRODUCED_IN(21);
+int statvfs64(const char* _Nonnull __path, struct statvfs64* _Nonnull __buf);
 
 /** Equivalent to fstatvfs(). */
-int fstatvfs64(int __fd, struct statvfs64* _Nonnull __buf) __INTRODUCED_IN(21);
+int fstatvfs64(int __fd, struct statvfs64* _Nonnull __buf);
 
 __END_DECLS
diff --git a/libc/include/sys/swap.h b/libc/include/sys/swap.h
index 9d016d4..474aed7 100644
--- a/libc/include/sys/swap.h
+++ b/libc/include/sys/swap.h
@@ -55,18 +55,14 @@
  * [swapon(2)](http://man7.org/linux/man-pages/man2/swapon.2.html) enables swapping.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int swapon(const char* _Nonnull __path,  int __flags) __INTRODUCED_IN(19);
+int swapon(const char* _Nonnull __path,  int __flags);
 
 /**
  * [swapoff(2)](http://man7.org/linux/man-pages/man2/swapoff.2.html) disables swapping.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int swapoff(const char* _Nonnull __path) __INTRODUCED_IN(19);
+int swapoff(const char* _Nonnull __path);
 
 __END_DECLS
diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index 06b2188..dc869da 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -66,8 +66,7 @@
  *
  * This method is for inspecting and debugging the property system, and not generally useful.
  */
-int __system_property_foreach(void (* _Nonnull __callback)(const prop_info* _Nonnull __pi, void* _Nullable __cookie), void* _Nullable __cookie)
-  __INTRODUCED_IN(19);
+int __system_property_foreach(void (* _Nonnull __callback)(const prop_info* _Nonnull __pi, void* _Nullable __cookie), void* _Nullable __cookie);
 
 /*
  * Waits for the specific system property identified by `pi` to be updated
diff --git a/libc/include/sys/timerfd.h b/libc/include/sys/timerfd.h
index aafcef2..de1f55b 100644
--- a/libc/include/sys/timerfd.h
+++ b/libc/include/sys/timerfd.h
@@ -50,10 +50,8 @@
  * timer file descriptor.
  *
  * Returns the new file descriptor on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int timerfd_create(clockid_t __clock, int __flags) __INTRODUCED_IN(19);
+int timerfd_create(clockid_t __clock, int __flags);
 
 /** The timerfd_settime() flag to use absolute rather than relative times. */
 #define TFD_TIMER_ABSTIME (1 << 0)
@@ -65,19 +63,15 @@
  * stops a timer.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int timerfd_settime(int __fd, int __flags, const struct itimerspec* _Nonnull __new_value, struct itimerspec* _Nullable __old_value) __INTRODUCED_IN(19);
+int timerfd_settime(int __fd, int __flags, const struct itimerspec* _Nonnull __new_value, struct itimerspec* _Nullable __old_value);
 
 /**
  * [timerfd_gettime(2)](http://man7.org/linux/man-pages/man2/timerfd_gettime.2.html) queries the
  * current timer settings.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
- *
- * Available since API level 19.
  */
-int timerfd_gettime(int __fd, struct itimerspec* _Nonnull __current_value) __INTRODUCED_IN(19);
+int timerfd_gettime(int __fd, struct itimerspec* _Nonnull __current_value);
 
 __END_DECLS
diff --git a/libc/include/sys/vfs.h b/libc/include/sys/vfs.h
index 18ae428..3579799 100644
--- a/libc/include/sys/vfs.h
+++ b/libc/include/sys/vfs.h
@@ -105,9 +105,9 @@
 #define XFS_SUPER_MAGIC       0x58465342
 
 int statfs(const char* _Nonnull __path, struct statfs* _Nonnull __buf);
-int statfs64(const char* _Nonnull __path, struct statfs64* _Nonnull __buf) __INTRODUCED_IN(21);
+int statfs64(const char* _Nonnull __path, struct statfs64* _Nonnull __buf);
 int fstatfs(int __fd, struct statfs* _Nonnull __buf);
-int fstatfs64(int __fd, struct statfs64* _Nonnull __buf) __INTRODUCED_IN(21);
+int fstatfs64(int __fd, struct statfs64* _Nonnull __buf);
 
 __END_DECLS
 
diff --git a/libc/include/sys/wait.h b/libc/include/sys/wait.h
index e6fb855..5208366 100644
--- a/libc/include/sys/wait.h
+++ b/libc/include/sys/wait.h
@@ -39,7 +39,7 @@
 
 pid_t wait(int* _Nullable __status);
 pid_t waitpid(pid_t __pid, int* _Nullable __status, int __options);
-pid_t wait4(pid_t __pid, int* _Nullable __status, int __options, struct rusage* _Nullable __rusage) __INTRODUCED_IN(18);
+pid_t wait4(pid_t __pid, int* _Nullable __status, int __options, struct rusage* _Nullable __rusage);
 
 /* Posix states that idtype_t should be an enumeration type, but
  * the kernel headers define P_ALL, P_PID and P_PGID as constant macros