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/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 7f9abd7..c126eba 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -22,8 +22,6 @@
 
 #include "signal.h"
 
-#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
-
 /*
  * For ARM syscalls, we encode the syscall number into the instruction.
  */
@@ -210,10 +208,8 @@
 	int err;
 
 	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
-	if (err == 0) {
-		sigdelsetmask(&set, ~_BLOCKABLE);
+	if (err == 0)
 		set_current_blocked(&set);
-	}
 
 	__get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
 	__get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);