Fixed Mac OS X build

include/SDL_opengl_glext.h

@@ -465,8 +465,13 @@ GLAPI void APIENTRY glBlendEquation (GLenum mode);
 #ifndef GL_VERSION_1_5
 #define GL_VERSION_1_5 1
 #include <stddef.h>
+#ifdef __MACOSX__
+typedef ssize_t GLsizeiptr;
+typedef ssize_t GLintptr;
+#else
 typedef ptrdiff_t GLsizeiptr;
 typedef ptrdiff_t GLintptr;
+#endif
 #define GL_BUFFER_SIZE                    0x8764
 #define GL_BUFFER_USAGE                   0x8765
 #define GL_QUERY_COUNTER_BITS             0x8864