Add versioning information to symbols.

Bug: http://b/28178111
Change-Id: I46bf95accd819f4521afb1173d8badcc5e9df31c
diff --git a/libc/include/grp.h b/libc/include/grp.h
index 3ae0d6e..9b4a518 100644
--- a/libc/include/grp.h
+++ b/libc/include/grp.h
@@ -55,11 +55,12 @@
 struct group* getgrnam(const char *);
 #if __POSIX_VISIBLE >= 200112 || __XPG_VISIBLE
 /* Android has thousands and thousands of ids to iterate through */
-struct group* getgrent(void) __attribute__((warning("getgrent is inefficient on Android")));
-void setgrent(void);
-void endgrent(void);
-int getgrgid_r(gid_t, struct group *, char *, size_t, struct group **);
-int getgrnam_r(const char *, struct group *, char *, size_t, struct group **);
+struct group* getgrent(void) __attribute__((warning("getgrent is inefficient on Android")))
+__INTRODUCED_IN(25);
+void setgrent(void) __INTRODUCED_IN(25);
+void endgrent(void) __INTRODUCED_IN(25);
+int getgrgid_r(gid_t, struct group*, char*, size_t, struct group**) __INTRODUCED_IN(24);
+int getgrnam_r(const char*, struct group*, char*, size_t, struct group**) __INTRODUCED_IN(24);
 #endif
 
 int getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups);