cSID portability modifications

Based on cSID and cSID-light by Hermit

Y U DO TIS?

I wanted a SID player for a hack project, and cSID looked small and nice, but the code was a bit hairy at places, so i though i'd try to clean it up a bit.

Y XALIOR DO TIS?

NextPi needed a stable snapshot to integrate into custom package management, CI, CD, and development toolchains.