support GL cores

[lifning]

lots of unknowns here with regard to whether pygame is up to the task - it has support for making a GL context i think, but whether that's sufficient for retro cores is something i have yet to discover :)

(we currently hardcode a variable for parallel-n64 to use the angrylion software renderer, which can be removed if we implement this)

[fregapple]

Have you had more of a look into this?