Pulse: use async API instead of simple API
Null driver: no audio driver with accurate timing
Add latency setting to alsa, pulse and android drivers
android: start and stop AudioTrack on audiobackend init/term
Simplify audiostream. Get rid of "none" option
The backend supports 44.1KHz and 48KHz (with resamping). The resampler
is not great, has some noise but no idea where it comes from.
This enables the switch port, since using SDL2 is the quickest way
to get audio working.
TODO: Add support in the cmake, once cmake is fixed at master/HEAD.
scribam