most of set_current_blocked() callers want SIGKILL/SIGSTOP removed from set

Only 3 out of 63 do not.  Renamed the current variant to __set_current_blocked(),
added set_current_blocked() that will exclude unblockable signals, switched
open-coded instances to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 17046cc..065e763 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -250,7 +250,8 @@
 extern int do_sigtimedwait(const sigset_t *, siginfo_t *,
 				const struct timespec *);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
-extern void set_current_blocked(const sigset_t *);
+extern void set_current_blocked(sigset_t *);
+extern void __set_current_blocked(const sigset_t *);
 extern int show_unhandled_signals;
 extern int sigsuspend(sigset_t *);