[POWERPC] Implement logging of unhandled signals

Implement show_unhandled_signals sysctl + support to print when a process
is killed due to unhandled signals just as i386 and x86_64 does.

Default to having it off, unlike x86 that defaults on.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 53a456e..c7314f9 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1221,7 +1221,7 @@
 };
 
 static ctl_table debug_table[] = {
-#ifdef CONFIG_X86
+#if defined(CONFIG_X86) || defined(CONFIG_PPC)
 	{
 		.ctl_name	= CTL_UNNUMBERED,
 		.procname	= "exception-trace",