The following fixes are backported from the Snes9x master branch:
- Release msu data and audio streams on exit, use unzClose when closing
- Fix MSU-1 channel swap on loop
- Ensure all MSU-1 reads are stereo channel aligned
- Clean up S9xMSU1Generate code
- Fix MSU1 swapping.
- Fix casting on MSU1 volume
- Get rid of "Unable to find msu file" console spam