SELinux: header generation may hit infinite loop

If a permission name is long enough the selinux class definition generation
tool will go into a infinite loop.  This is because it's macro max() is
fooled into thinking it is dealing with unsigned numbers.  This patch makes
sure the macro always uses signed number so 1 > -1.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

scripts/selinux/genheaders/genheaders.c

@@ -13,7 +13,7 @@ struct security_class_mapping {
 #include "classmap.h"
 #include "initial_sid_to_string.h"
 
-#define max(x, y) ((x > y) ? x : y)
+#define max(x, y) (((int)(x) > (int)(y)) ? x : y)
 
 const char *progname;