Allow a way to specify the portaudio location

It would be nice to be able to specify the location of the portaudio lib for people that want to use a specific location and/or version. At present the code just uses whatever ctypes find_library discovers or reverts to the provided _sounddevice_data folder.

Downsides:

1. it’s often unnecessary to provide portaudio (at least on *nix systems)
2. this isn’t the location that the rest of the OS expects things. That causes problems for packaging the lib into an app. For example to wrap sounddevice up into an application bundle on Mac (e.g. py2app) the dylib files really should go into the Contents/Frameworks folder. If the app is going to be code-signed to verify it was from a trusted developer then the dylibs MUST go into the frameworks folder

I wonder if we could have something like a check for an environment variable first, like os.environ[‘SD_PORTAUDIO’] ?

[j9ac9k]

Thanks for making this library, you helped me regain my sanity with trying to replicate the sounddevice.OutputStream functionality with the Qt framework using QAudioOutput (after weeks of trying I gave up, and stumbled across sounddevice).

Also in case you’re curious, with this PR, libportaudio.dylib is placed in a part of the .app bundle where the bundle can be codesigned and notarized.

[mgeier]

Thanks @j9ac9k!