Merge from NPTL branch.

libc/signal/sigaction.c

@@ -102,5 +102,7 @@ __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
 
 #endif
 
+#ifndef LIBC_SIGACTION
 hidden_weak_alias(__libc_sigaction,__sigaction)
 weak_alias(__libc_sigaction,sigaction)
+#endif