Fixed bug 3791 - SDL_bits.h: __builtin_clz is supported in gcc >= 3.4

Ozkan Sezer

__builtin_clz is supported in gcc >= 3.4. The following patchlet adjusts
SDL_bits.h for it.

include/SDL_bits.h

@@ -60,7 +60,7 @@ extern _inline int _SDL_clz_watcom (Uint32);
 SDL_FORCE_INLINE int
 SDL_MostSignificantBitIndex32(Uint32 x)
 {
-#if defined(__GNUC__) && __GNUC__ >= 4
+#if defined(__GNUC__) && (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
     /* Count Leading Zeroes builtin in GCC.
      * http://gcc.gnu.org/onlinedocs/gcc-4.3.4/gcc/Other-Builtins.html
      */