[Openal] Configure the number of speakers upon initialization

[michelle]

Currently, I am using a simple call to alutInit() in order to start
using OpenAL. While this perfectly takes into account the number of
speakers the sound card support - e.g. I will get stereo output for a
stereo card, 5.1 output for a 5.1 card, etc. - it is getting
problematic when I have a 5.1 card but only stereo speakers connected
to them.

Apparently, OpenAL creates a 5 channel output in this case, but as I
only have 2 speakers, I hear sounds only from certain angles. On
Windows, I would have assumed that going to Control Panel > Sounds and
Audio Devices > Advanced, and setting "Speaker setup" to "Desktop
stereo speakers" might cure this problem. However, it does not seem to
be taken into account by OpenAL.

As such, what can I do upon initialization to inform OpenAL about the
amount of speakers that are actually connected to the system? Will I
need to tell users to provide this number manually?