Fix audio device sharing in GNU/Linux

Ignore-this: 1faaa50ead8a54ff5e622df9b4c55fd

Credits go to the SIP-Communicator project.

darcs-hash:20100531134709-56b4d-88f4f580b3efbcb3ee89194c747c404c5da84775
Improve documentation

Ignore-this: a5e5f8f3529902dc41c32ad04860cf17

darcs-hash:20100531214516-58252-be42f631356eeece9cd6f3260d7e8432ba757352