Add platform specific version tags.

Some functions were added at different times on different platforms.
This should hopefully get most of them.

Bug: http://b/28178111
Change-Id: I85fdf92779a2f3277e9b537c6bfc7216790c607a
diff --git a/libc/include/sys/resource.h b/libc/include/sys/resource.h
index 74e903f..3187420 100644
--- a/libc/include/sys/resource.h
+++ b/libc/include/sys/resource.h
@@ -53,7 +53,8 @@
 
 extern int getrusage(int, struct rusage*);
 
-extern int prlimit(pid_t, int, const struct rlimit*, struct rlimit*) __INTRODUCED_IN(24);
+extern int prlimit(pid_t, int, const struct rlimit*, struct rlimit*) __INTRODUCED_IN_32(24)
+  __INTRODUCED_IN_64(21);
 extern int prlimit64(pid_t, int, const struct rlimit64*, struct rlimit64*) __INTRODUCED_IN(21);
 
 __END_DECLS