Sound Refactor: fixing music streaming and sample priorities

I think things are working now. There was a big tradeoff with this: now the samples are pre-rendered and stored in memory, rather than streamed in real time. Not sure if this is a big deal but it could be a gotcha later if the memory usage is rather high.

On the bright side I'm pretty sure playing sound with priorities works more accurately now.

Oh, and multiple .NSF files are supported at the same time -- that's cool.