Update snes9x code from 1.53 to 1.6.0.

Notable differences from upstream:
* Did not use the same #include setup for the new byuu apu and instead chose to do things more traditionally, as the latter is also much easier to deal with in Visual Studio than just including .cpp files into other .cpp files...
* MSU1 support not included (I see no need for this in a plugin meant to be used for original SNES music).
* The dynamic rate control on the APU not included (I also see no need for it in this plugin).
* The extra resamplers I added in were removed as the original hermite resampler was folded into a single non-inhertiable resampler.
* Bits of cleanup.