Fixed use of stun_servers setting in sip_audio_session

Ignore-this: c34d9fdc12ee1bdb2121bc5802ec8b4d

darcs-hash:20090609103834-1e3d8-b61b6be5d95eb719571b55680f09fd2c7912bd16
Added item to TODO

darcs-hash:20090609131105-58103-45180524455b99b6f0470082aad7c9f94bd6bc17