pjsip: Let opus adjust itself for voice / music signals

Ignore-this: 438b032580bf1a927c0d0218894c2983

darcs-hash:20130723090502-56b4d-d4a4ee321a54176d390a9c12ca870cafcf09195f
pjsip: Adjusted acoustic gain control levels to improve echo cancelling

Ignore-this: 590a1d893a949ae62ab4ece01323c93a

darcs-hash:20130724145340-b22ec-4538c115c8229a0bcb7de822dd0fb75d3b9a4dfb
pjsip: Increased echo canceller aggressiveness

Ignore-this: 6350431561c5f66228033880176944c7

darcs-hash:20130724145451-b22ec-66a438d29529ef0ac508549a86567e654cf21c8a