Add versioning information to symbols.

Bug: http://b/28178111
Change-Id: I46bf95accd819f4521afb1173d8badcc5e9df31c
diff --git a/libc/include/signal.h b/libc/include/signal.h
index 5679402..6b127b8 100644
--- a/libc/include/signal.h
+++ b/libc/include/signal.h
@@ -72,8 +72,8 @@
 /* We take a few real-time signals for ourselves. May as well use the same names as glibc. */
 #define SIGRTMIN (__libc_current_sigrtmin())
 #define SIGRTMAX (__libc_current_sigrtmax())
-extern int __libc_current_sigrtmin(void);
-extern int __libc_current_sigrtmax(void);
+extern int __libc_current_sigrtmin(void) __INTRODUCED_IN(21);
+extern int __libc_current_sigrtmax(void) __INTRODUCED_IN(21);
 
 extern const char* const sys_siglist[];
 extern const char* const sys_signame[]; /* BSD compatibility. */
@@ -125,11 +125,14 @@
 extern int sigsuspend(const sigset_t*) __nonnull((1));
 extern int sigwait(const sigset_t*, int*) __nonnull((1, 2));
 
-extern int sighold(int) __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead")));
-extern int sigignore(int) __attribute__((deprecated("use sigaction() instead")));
-extern int sigpause(int) __attribute__((deprecated("use sigsuspend() instead")));
-extern int sigrelse(int) __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead")));
-extern sighandler_t sigset(int, sighandler_t) __attribute__((deprecated("use sigaction() instead")));
+extern int sighold(int)
+  __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead"))) __INTRODUCED_IN(25);
+extern int sigignore(int) __attribute__((deprecated("use sigaction() instead"))) __INTRODUCED_IN(25);
+extern int sigpause(int) __attribute__((deprecated("use sigsuspend() instead"))) __INTRODUCED_IN(25);
+extern int sigrelse(int)
+  __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead"))) __INTRODUCED_IN(25);
+extern sighandler_t sigset(int, sighandler_t) __attribute__((deprecated("use sigaction() instead")))
+__INTRODUCED_IN(25);
 
 extern int raise(int);
 extern int kill(pid_t, int);
@@ -137,15 +140,15 @@
 
 extern int sigaltstack(const stack_t*, stack_t*);
 
-extern void psiginfo(const siginfo_t*, const char*);
-extern void psignal(int, const char*);
+extern void psiginfo(const siginfo_t*, const char*) __INTRODUCED_IN(21);
+extern void psignal(int, const char*) __INTRODUCED_IN(21);
 
 extern int pthread_kill(pthread_t, int);
 extern int pthread_sigmask(int, const sigset_t*, sigset_t*);
 
-extern int sigqueue(pid_t, int, const union sigval);
-extern int sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*);
-extern int sigwaitinfo(const sigset_t*, siginfo_t*);
+extern int sigqueue(pid_t, int, const union sigval) __INTRODUCED_IN(23);
+extern int sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*) __INTRODUCED_IN(23);
+extern int sigwaitinfo(const sigset_t*, siginfo_t*) __INTRODUCED_IN(23);
 
 __END_DECLS