Closes #1413Closes#1414
This commit addresses issues with building PortMixer
using the upstream version of PortAudio.
The resulting solution allows:
* To build Linux with the vanilla PortAudio.
* To build Windows with the vanilla PortAudio, but the notable exceptions:
* for PortMixer to work on MME - PA 19.7.0 is required; only static linking is supported. A patch is available to allow dynamic linking;
* for PortMixer to work on DirectSound - the patch is always required.
Remove nyquist autotools
