wip/portaudio 19.7.0 NetBSD

TODO: Adjust the following lines from README.md

# PortAudio - portable audio I/O library

PortAudio is a portable audio I/O library designed for cross-platform support of audio. It uses either a callback mechanism to request audio processing, or blocking read/write calls to buffer data between the native audio subsystem and the client. Audio can be processed in various formats, including 32 bit floating point, and will be converted to the native format internally.

## Documentation:

* Documentation is available at http://www.portaudio.com/docs/ * Or at `/doc/html/index.html` after running Doxygen. * Also see `src/common/portaudio.h` for the API spec. * And see the `examples/` and `test/` directories for many examples of usage. (We suggest `examples/paex_saw.c` for an example.)

For information on compiling programs with PortAudio, please see the tutorial at:

http://portaudio.com/docs/v19-doxydocs/tutorial_start.html ...