[openal] Final testing for OpenAL Soft 1.17

[Chris Robinson]

OpenAL Soft's HRTF extension was recently finalized in Git. I'm not 
aware of anything more that needs to be done before the 1.17 release, so 
it's expected to be soon.

If you have any apps you want to test, please do. If there's any 
OSs/systems you want to make sure it builds and works for, please do. If 
there's any important bugs you're aware of, please mention it, or put it 
on the issue tracker on the github:
https://github.com/kcat/openal-soft/issues
Even if there's some feature you've been wanting, feel free to mention 
it (worst case, it waits until after 1.17).