Changes in this version:
-Lots of optimisations! Factored out more division, use reciprocal table, move more code to IWRAM. Offers around a 15-25% improvement in FPS.
-Some memory savings. There's still a couple of levels in Plutonia that won't load, (Map 23 & 28).
-Added framerate display. (Which can be accessed via a cheat. Thanks KipyKip. Why didn't I think of that!?) It replaces your current weapon ammo display and is in 10th's. So 234 = 23.4FPS.
-Fixed cyberdemon and spiderdemon not being drawn at distances over 1280 units.
-Allowed PC build for debugging with MSVC compiler too. (Use 32bit. I don't think it works 64bit due to struct alignment.)