Update header versions for NDK platform fixes.

Bug: http://b/28178111
Change-Id: Icd638673b409aa43a91490f77c6b4d79c9ea20d9
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 71764ae..7deca95 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -90,7 +90,7 @@
 extern pid_t  getppid(void);
 extern pid_t  getpgrp(void);
 extern int    setpgrp(void);
-extern pid_t  getsid(pid_t __pid) __INTRODUCED_IN(21);
+extern pid_t  getsid(pid_t __pid) __INTRODUCED_IN(17);
 extern pid_t  setsid(void);
 
 extern int execv(const char* __path, char* const* __argv);
@@ -127,7 +127,7 @@
 
 extern int access(const char* __path, int __mode);
 extern int faccessat(int __dirfd, const char* __path, int __mode, int __flags)
-  __INTRODUCED_IN(21);
+  __INTRODUCED_IN(16);
 extern int link(const char* __oldpath, const char* __newpath);
 extern int linkat(int __olddirfd, const char* __oldpath, int __newdirfd,
                   const char* __newpath, int __flags) __INTRODUCED_IN(21);
@@ -285,7 +285,7 @@
 extern ssize_t __readlinkat_chk(int dirfd, const char*, char*, size_t, size_t) __INTRODUCED_IN(23);
 __errordecl(__readlinkat_dest_size_error, "readlinkat called with size bigger than destination");
 __errordecl(__readlinkat_size_toobig_error, "readlinkat called with size > SSIZE_MAX");
-extern ssize_t __readlinkat_real(int dirfd, const char*, char*, size_t) __RENAME(readlinkat);
+extern ssize_t __readlinkat_real(int dirfd, const char*, char*, size_t) __RENAME(readlinkat) __INTRODUCED_IN(21);
 
 extern int getdomainname(char*, size_t) __INTRODUCED_IN_FUTURE;
 extern int setdomainname(const char*, size_t) __INTRODUCED_IN_FUTURE;