xstring: shorter, safer implementation of getExtension
Windows build fix

Turns out the string functions I removed were used, but missed my grep.
Doesn't matter though, since these are just doing the same thing as
getExtension
emufile: stylistic cleanup
[unfinished commit] Begin moving audio over to a new interface (audio currently non-functional for many builds)

Currently works for the OSX and Windows stand-alone builds.