Change the minimal SSP buffer size.

https://bugs.gentoo.org/484714
--- a/gcc/params.def	2016-03-30 09:47:40.000000000 +0200
+++ b/gcc/params.def	2016-09-19 12:56:58.443179039 +0200
@@ -673,7 +673,7 @@ DEFPARAM (PARAM_INTEGER_SHARE_LIMIT,
 DEFPARAM (PARAM_SSP_BUFFER_SIZE,
 	  "ssp-buffer-size",
 	  "The lower bound for a buffer to be considered for stack smashing protection.",
-	  8, 1, 0)
+	  4, 1, 0)
 
 DEFPARAM (PARAM_MIN_SIZE_FOR_STACK_SHARING,
 	  "min-size-for-stack-sharing",