Macro cleanups for selecting which decoders to compile in. Before this was hacked for Apple vs. Android. But now it is Apple vs. whatever to be a little more flexible. If Apple, Core Audio will always be picked for WAV/MP3. This could be more flexible, but for shipping apps, there are not a lot of compelling reasons to not use Core Audio when it is available. Ogg Vorbis/Tremor are in common areas so it is directly selectable since Core Audio does not support Ogg. You are responsible for not trying to compile/link both Vorbis/Tremor at the same time. They are mutually exclusive.