OpenAL back-end: repost for reconsideration

[Stefan Dösinger]

The problem with the openal32.dll -> libopenal.so wrapper was that it broke
some games, and we never debugged why. If anyone wants to continue this
development I think this wrapper library is something that would be highly
welcome.

As for the winmm driver, Roderick pretty much said it. We don't need another
half baked sound backend, the effort should instead be put into making sure
we have one properly working one for each platform(Alsa for Linux, coreaudio
on the mac, not sure about *BSD and Solaris)