SDL_test_md5.h: fix MD5UINT4 type to be really 32 bits.

include/SDL3/SDL_test_md5.h

@@ -65,7 +65,7 @@ extern "C" {
 /* ------------ Definitions --------- */
 
 /* typedef a 32-bit type */
-  typedef unsigned long int MD5UINT4;
+  typedef Uint32 MD5UINT4;
 
 /* Data structure for MD5 (Message-Digest) computation */
   typedef struct {