pjsip: Adjusted some opus codec parameters

Ignore-this: df5df68e5dd22e7910ca14d7cbd7ca72

- Set complexity to 10
- Enabled inband FEC
- Consider 5% packet loss

darcs-hash:20130710154346-56b4d-d028cc579db993554543a4448ce06bd3ed922529
Set default echo tail length to 15

Ignore-this: 3542d7b8bffaaf9d09cabb8acae401f1

darcs-hash:20130710154632-56b4d-a48707586b7201bed65fd179bd4ac7cebc7e6610
Build PJSIP silently

Ignore-this: b42198b3b7af08a16f8c4e37f4549d7b

darcs-hash:20130711100241-56b4d-4acd288b60ff4619f2bc50b7e1ac84c966b553a1