SDL_opengl: Fix Mac build for SDK 10.9 too.

include/SDL_opengl.h

@@ -51,7 +51,10 @@
 #endif
 #if defined(__MACOSX__)
 #include <stddef.h>             /* Needed for ptrdiff_t */
+/* Hack to prevent duplicate definition of GLsizeiptrARB and GLintptrARB in <OpenGL/gltypes.h> */
+#define GL_ARB_vertex_buffer_object 1
 #include <OpenGL/gl.h>          /* Header File For The OpenGL Library */
+#undef GL_ARB_vertex_buffer_object
 #define __X_GL_H
 #else
 #include <GL/gl.h>              /* Header File For The OpenGL Library */

include/SDL_syswm.h

@@ -83,7 +83,7 @@ struct SDL_SysWMinfo;
 
 #if defined(SDL_VIDEO_DRIVER_COCOA)
 #ifdef __OBJC__
-#include <Cocoa/Cocoa.h>
+@class NSWindow;
 #else
 typedef struct _NSWindow NSWindow;
 #endif