Seperate glX from HAVE_OPENGL, for platforms that have both an X server and a more official way to do OpenGL, explicitly check for glX on Mac OS X, and use SDL_LoadObject for platforms that have glX but don't have dlopen().

#ifndef _SDL_SYSMUTEX_C_H_
#define _SDL_SYSMUTEX_C_H_

struct SDL_mutex {
	pth_mutex_t mutexpth_p;
};

#endif /* _SDL_SYSMUTEX_C_H_ */