generic sys_sigaction() and compat_sys_sigaction()

conditional on OLD_SIGACTION/COMPAT_OLD_SIGACTION

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 0b6878e..e28e8d4 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -269,6 +269,15 @@
 	__sigrestore_t ka_restorer;
 #endif
 };
+ 
+#ifdef CONFIG_OLD_SIGACTION
+struct old_sigaction {
+	__sighandler_t sa_handler;
+	old_sigset_t sa_mask;
+	unsigned long sa_flags;
+	__sigrestore_t sa_restorer;
+};
+#endif
 
 extern int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, struct pt_regs *regs, void *cookie);
 extern void signal_delivered(int sig, siginfo_t *info, struct k_sigaction *ka, struct pt_regs *regs, int stepping);