Documentation, more libraries, and a new ScummVM build

A quick update:

• I doxygenized the code and you can find the resulting documentation here. There's a boatload of information on the various interfaces available, so if you have any interest in joining the fun, check it out.
• There are four new libraries in the 3rdparty directory: libmad, libogg, libvorbis, and Tremor.
• There is a new ScummVM build with zlib, MAD, and Tremor enabled, so you can play your compressed games now.

Have fun!