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/syscalls.h b/include/linux/syscalls.h
index 1c4938b..02b0450 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -385,6 +385,11 @@
 asmlinkage long sys_sigsuspend(int unused1, int unused2, old_sigset_t mask);
 #endif
 
+#ifdef CONFIG_OLD_SIGACTION
+asmlinkage long sys_sigaction(int, const struct old_sigaction __user *,
+				struct old_sigaction __user *);
+#endif
+
 #ifndef CONFIG_ODD_RT_SIGACTION
 asmlinkage long sys_rt_sigaction(int,
 				 const struct sigaction __user *,