caedes and some other people will probably kill me for this, but I'm the
idiot who has to maintain the code. And that's much easier if it's in a
readable und writeable state.
Copied and adapted (hopefully) all relevant code from Q2Pro.
Did some small refactorings when needed.
Still TODO:
* Adapt Makefile
* OGG support when using OpenAL
* A cvar that switches between OpenAL and DMA/SDL
* Actually compiling and testing this stuff ;)