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/s390/kernel/compat_signal.c

@@ -580,11 +580,7 @@ void handle_signal32(unsigned long sig, struct k_sigaction *ka,
 		ret = setup_frame32(sig, ka, oldset, regs);
 	if (ret)
 		return;
-	block_sigmask(ka, sig);
-	/*
-	 * Let tracing know that we've done the handler setup.
-	 */
-	tracehook_signal_handler(sig, info, ka, regs,
+	signal_delivered(sig, info, ka, regs,
 				 test_thread_flag(TIF_SINGLE_STEP));
 }