MD2/MD3 support rewritten + optimizations [GCC port]

This is SSN's !2 (closed) merge that adds MD3 support and OpenGL optimizations -- made to work with GCC and approved by buildbots.

We're in a tricky spot because Wolfy has said that SSN's branch crashes, whereas SSN said that my branch crashes. So I want to get this version in front of your eyes and see how broken it is:

• Does it work on Intel, nVidia, and AMD?
• Does it work when compiled from GCC?
• Does it work when compiled from VS?

I'd propose that neither version gets merged until it works for everyone -- SSN included. The expected result is that both branches work identically -- just that mine compiles for GCC.

Test MD3: KartMD3.zip

• Merge into your current MD2 folder -- adds MD3 subfolder
• In KMD2.dat, comment out the existing SONIC line and add: SONIC MD3/PLAY.md3 3.0 0.0
• Animations for the model are jittery -- I think that's intentional.