pjsip: Added opus codec support

Ignore-this: fde7af52a87dca6c3b681d1dffb570a1

darcs-hash:20130611151533-56b4d-402eb7e49bea660381558e9e071283d0ad87c206
Enabled opus codec

Ignore-this: b39de973546dd8139cf37b3af08f9b1d

darcs-hash:20130612123331-56b4d-d4ab3e8338cc1f236d3febc1b266d6a556cd8c83
Use WebRTC AEC by default

Ignore-this: f098cf0c45a5ceb464e700bf82648c6b

darcs-hash:20130612123338-56b4d-a5dbd99568ab6e635b535b6640ba3f715c20e214
Disabled narrowband speex

Ignore-this: 45fdd7b0a93c219e35d036bc8895482f

darcs-hash:20130612165132-56b4d-b4f53093ad10f94449026ab93e108128efb701f9
Start RTP transport when AudioTransport.start is called

Ignore-this: 96f2b617d18c0c537779c92edf73520f

darcs-hash:20130613133140-56b4d-e1c8191feb643337e6326436806b27ea56efc664
Fixed starting media stream if ICE fails early

Ignore-this: 8f6ac9600f6eafb42a43a47df8e6102c

If ICE fails early (the SDP is malformed, for example), RTPTransportICENegotiationDidFail
is received before stream.start is called

darcs-hash:20130613133207-56b4d-1bee867fbc9b64c9e6d79bbf0a741530613a144e