Fix compilation of the sumversion "script"

http://bugs.gentoo.org/show_bug.cgi?format=multiple&id=226169

Index: linux-2.6.21/scripts/mod/sumversion.c
===================================================================
--- linux-2.6.21.orig/scripts/mod/sumversion.c	2007-04-26 04:08:32.000000000 +0100
+++ linux-2.6.21/scripts/mod/sumversion.c	2010-05-13 14:41:31.777882280 +0100
@@ -7,6 +7,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <string.h>
+#include <limits.h>
 #include "modpost.h"
 
 /*