Added SOATAG_RTP_SELECT(), SOATAG_RTP_SORT() and SOATAG_RTP_MISMATCH() for
indicating sdp negotiation preferences. Select the RTP codec according to the
preferences when sending or processing the answer.

darcs-hash:20051113184249-65a35-178ebced49dfaf46e24518c49ed2b049118015ae.gz