crc32: Fixed include path.

src/stdlib/SDL_crc32.c

@@ -18,7 +18,7 @@
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
-#include "../../SDL_internal.h"
+#include "../SDL_internal.h"
 
 #include "SDL_stdinc.h"