Add MSADPCM support.

Okay, take two on this one. This time, not organized in an embarrassingly terrible way.

I added ADPCM support with a decoder I made, MSADPCMToPCM.

It's a noticeable hang, since we're basically decoding every ADPCM file in the Bank to PCM for our various backends, but that's probably about as good as it's going to get.

I've got it working in my current port, but testing of this against other compressed XACT data would be highly appreciated. I recall Murudai needing this for Solar 2, anybody know a good way to get in touch with him?

This should also be fully cross-platform, so I've added the decoder to all of the project files as well.