Add pjmedia synchronizer port (for audio device).

[nanang]

It is a common problem that audio device does not always provide a smooth clock for application, therefore the application may suffer from jitter, burst, or even clock skew/drift. Processing audio frames in such 'messy' clock will just increase the complexity. So, before delivering the stream to other components, it could be very helpful to tidy up the clock at the very beginning (in the audio device).

[nanang]

In r2747:

• Added pjmedia synchronizer port.
• Updated affected components, i.e: sound port, AEC, conference bridge.

[nanang]

In r2748:

• Fixed bug in conf bridge create_on_port() (bug of r2747).
• Updated sound port to instantiate sync port only when audio format is PCM.

[bennylp]

In r2751:

• updated VS6, Makefile, and Symbian .mmp project files with new file sync_port.c.

[nanang]

In r2755:

• Reverted back all changes in this ticket: r2747, r2748, r2751.

Decided to restart the project with a better preparation, as problems met are not as simple as I thought. Current and further changes are considered to be (very) major, so it may need to be done in a separate branch.

[nanang]

History of all changes on this ticket before r2755, including uncomitted patch.

[nanang]

TeluuCon? 2018: Audio device clock issues such as clock skew should have been handled now, e.g: delay buffer with its WSOLA can shrink/expand wave, jitter buffer has discard algo.