PulseAudio latency reporting

[gavv]

We should report roc sink and roc sink input latency to PulseAudio so it could be taken into account when PulseAudio calculates the overall latency.

[gavv]

Related: #18.

[gavv]

Important:

• PA modules should report the overall latency, including the network part, calculated from receiver reports;
• We should test that video players which support lip sync will handle the reported latency properly.