Unix socket support

[pgaskin]

• [x] Ensure Unix socket creation works.
• [x] Figure out a way to patch the system-wide local state dir to use ProgramData.
• [x] Test the user-specific state dir.
• [x] Fix auto-detection.
• [ ] Add options to the installer?

Split from #2

[pgaskin]

The existing Unix socket code in PA should work fine in theory.

https://github.com/freedesktop/pulseaudio/blob/master/src/modules/module-protocol-stub.c https://github.com/freedesktop/pulseaudio/blob/master/src/pulsecore/socket.h https://github.com/freedesktop/pulseaudio/blob/master/src/pulsecore/socket-util.c

But, when module-native-protocol-unix is loaded with pa-win32 v2, it gives:

(9537.920|   0.002) E: [(null)] ../../src/pulseaudio/src/modules/module-protocol-stub.c: Failed to remove stale UNIX socket 'C:\Windows\ServiceProfiles\LocalService\AppData\Local\PulseAudio\.config\pulse\WIN-TIF3CSSABRF-runtime\native': No such file or directory
(9537.920|   0.000) E: [(null)] ../../src/pulseaudio/src/pulsecore/module.c: Failed to load module "module-native-protocol-unix" (argument: ""): initialization failed.

This is because the path gets trimmed to C:\Windows\ServiceProfiles\LocalService\AppData\Local\PulseAudio\.config\pulse\WIN-TIF3CSSABRF-runtime\nati.

This shouldn't be an issue after I change the runtime directory for the system instance to ProgramData (which it'll have to be anyways, since all users would need to be able to access it).

[pgaskin]

Done in 8fc1b1099f8341931eb6af3b7d175421c3929c87.