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>
diff --git a/scripts/selinux/genheaders/genheaders.c b/scripts/selinux/genheaders/genheaders.c
index 771b86f..2462696 100644
--- a/scripts/selinux/genheaders/genheaders.c
+++ b/scripts/selinux/genheaders/genheaders.c
@@ -13,7 +13,7 @@
 #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;