Add versioning information to symbols.

Bug: http://b/28178111
Change-Id: I46bf95accd819f4521afb1173d8badcc5e9df31c
diff --git a/libc/include/netinet/in.h b/libc/include/netinet/in.h
index 5f3d11f..b524b05 100644
--- a/libc/include/netinet/in.h
+++ b/libc/include/netinet/in.h
@@ -49,8 +49,8 @@
 
 int bindresvport(int, struct sockaddr_in*);
 
-extern const struct in6_addr in6addr_any;
-extern const struct in6_addr in6addr_loopback;
+extern const struct in6_addr in6addr_any __INTRODUCED_IN(24);
+extern const struct in6_addr in6addr_loopback __INTRODUCED_IN(24);
 
 __END_DECLS