Portaudio v19 DirectSound:
support for WAVEFORMATEXTENSIBLE
This is an early copy of v19 (DirectSound) modified to support
multi-channel rendering using WAVEFORMATEXTENSIBLE.
implementation should also support the MME API as well;
and of course, also support recording! I never got around to it...
All changes are marked RWD_WAVEX_IMPL
This code is used in the command-line soundfile player "paplay"
in the CDP Multi-Channel Toolkit.