Renamed AudioInstance to AudioSourceInstance, to mirror Filter and FilterInstance
Split the huge soloud.cpp into a bunch of files.
Merge pull request #2 from tv-s/master

WinMM: fix random crashing when shutting down
Reorganized directory structure.
Merge branch 'master' of https://github.com/jarikomppa/soloud
Changed "aStereo" to "aChannels" in filters, moved filters from the "piano" example to their own folder.
De-interlaced audio samples to simplify processing (especially when we get more than 2 channels)
A rather huge change, so there's bound to be some bugs.
Ditched the rather pointless "load channel N as mono" options from the wav/ogg loaders