* Revert to using literal function pointers for GL extensions rather than PFN* typedefs as some platforms' headers are broken enough that they prevent SDL_opengl.h from fixing things up if the PFN* typedefs are missing
* Revert to using literal function pointers for GL extensions rather than PFN* typedefs as some platforms' headers are broken enough that they prevent SDL_opengl.h from fixing things up if the PFN* typedefs are missing