Fix up CMakeLists.txt

[SteelT1]

Fixes up CMakeLists.txt so the rest of the files is in the proper sections, honestly not sure if this is right, but it works and builds.

[wyatt8740]

Um, looking at the commit, I'm not sure what's different.
A lot of the libs are still basically in a 'miscellaneous' section, and I think I already did the gens/MAME YM2612 thing.

Thanks for the request, though. My car got screwed up by a minivan the other week, and I'm going to get it back from a body shop today, but once that's taken care of I can look at this in more detail.

I'm also new to this whole 'having people make pull requests' thing - usually my projects don't get that much attention!-- So I'm sorry if I'm handling these badly. I'm thankful that someone's helping out. :)

[SteelT1]

The gens/MAME YM2612 thing was changed so before it checks if USE_GENS is enabled, it checks if USE_GME_VGM or USE_GME_GYM is enabled. Also put the remaining stuff under if (USE_GME_VGM), not sure if that's correct and nothing will break from doing this, though.