ao_wasapi0: Support device enumeration, selection and WASAPI shared mode

Also includes a different sample format guessing algorithm for exclusive mode, which only accepts hardware-native
formats and doesn't let people get a list of them.

WASAPI shared mode lets ao_wasapi0 work without killing the sound of all other running programs. If the AO
is stable enough, it could be bumped to be ahead of dsound in the priority list.