new helper: signal_delivered()

Does block_sigmask() + tracehook_signal_handler();  called when
sigframe has been successfully built.  All architectures converted
to it; block_sigmask() itself is gone now (merged into this one).

I'm still not too happy with the signature, but that's a separate
story (IMO we need a structure that would contain signal number +
siginfo + k_sigaction, so that get_signal_to_deliver() would fill one,
signal_delivered(), handle_signal() and probably setup...frame() -
take one).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/ia64/kernel/signal.c

@@ -419,12 +419,7 @@ handle_signal (unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
 	if (!setup_frame(sig, ka, info, sigmask_to_save(), scr))
 		return 0;
 
-	block_sigmask(ka, sig);
-
-	/*
-	 * Let tracing know that we've done the handler setup.
-	 */
-	tracehook_signal_handler(sig, info, ka, &scr->pt,
+	signal_delivered(sig, info, ka, &scr->pt,
 				 test_thread_flag(TIF_SINGLESTEP));
 
 	return 1;