[Openal] Several capture devices in parallel

[Daniel PEACOCK]

> You'll have to use it directly and bypass the OpenAL32 router though,
> since that seems to enforce one capture device at a time (unless that's
been
> changed?).

Didn't know about that bug.  Yeah it looks like the router is only
supporting one capture device ... and the router is the one responsible for
returning the duplicate ALCdevice pointers on repeated calls to
alcCaptureOpenDevice!   Two bugs that need fixing ...

Dan