Fixed revert of e7c7ebf665.

Fixes #269.

deps/GL/glext.h

@@ -4135,8 +4135,16 @@ GLAPI void APIENTRY glVertexBlendARB (GLint count);
 
 #ifndef GL_ARB_vertex_buffer_object
 #define GL_ARB_vertex_buffer_object 1
+/* HACK: This is a workaround for gltypes.h on OS X 10.9 defining these types as
+ *       long instead of ptrdiff_t
+ */
+#if defined(__APPLE__)
+typedef long GLsizeiptrARB;
+typedef long GLintptrARB;
+#else
 typedef ptrdiff_t GLsizeiptrARB;
 typedef ptrdiff_t GLintptrARB;
+#endif
 #define GL_BUFFER_SIZE_ARB                0x8764
 #define GL_BUFFER_USAGE_ARB               0x8765
 #define GL_ARRAY_BUFFER_ARB               0x8892