Mods for supertuxkart and quake3

Hi. Thanks for this library - it's awesome! I've just been trying it out on an ODroid board, and I found that supertuxkart wasn't loading any textures. It turns out it was due to what I think was a bug in the texture swizzling code: https://github.com/gfwilliams/glshim/commit/2b264dc7e554ba945d253a7c44aedae49b7e999f

Basically it never returned the new colour format flags even though it set them.

I also found that (unsurprisngly) openarena/ioquake3 wasn't working, and discovered that glArrayElement wasn't implemented. I've now done this and quake3 is now playable (however it's a bit slow and only the light textures are applied - presumably due to the lack of multitexturing): https://github.com/gfwilliams/glshim/commit/4fb80672fb9fac4b73d3ac4c7b4f932421ec2cc8

Also, because I have no idea how to use GitHub, sadly there's another commit which disables mipmapping (because I was having troubles with textures not showing and I figured I'd rather just have un-mip-mapped textures!). Presumably you could remove that pretty easily though.

Hope that helps!

- Gordon