Added check for AMD x86-64 ("Hammer") architecture in byte order determination.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40531

include/SDL_byteorder.h

@@ -44,6 +44,7 @@ static char rcsid =
      defined(__arm__) || \
     (defined(__mips__) && defined(__MIPSEL__)) || \
      defined(__SYMBIAN32__) || \
+     defined(__x86_64__) || \
      defined(__LITTLE_ENDIAN__)
 #define SDL_BYTEORDER	SDL_LIL_ENDIAN
 #else