Jack support (now ready!)

[billythehippo]

Hello! This is more news than issue.
We (our sound engineering team) have realized the jack support for Emitter.
To do this we have made one more callback process: now there are jack_process_cb_rx (the original one but renamed) and jack_process_cb_tx (the new one), also the jack_read function with blocking process by mutex to prevent underruns. To debug these we have reworked the emitter's reaction to invalid packets: now it continues but ignores the invalid packet and gives the message about it with the counter of underruns.
Also now the ports of Emitter are named as Captures and the ports of Receptor are named as playback. We have switched off the jack auto connect action because of some bugs. Maybe it will be necessary to give jack ports the JackPortIsPhysical flag to make them a virtual sound card (as in zita-njbridge).
And we have made a bug fix when the buffer_size is calculated: now it's based not on initial value (zeros) but on backend's ones.

But for all of these some tests and code review are required. Please, help with it. Thanks!

[djmasa1]

That's great. Where do we get it? The current master version still has it disabled. I removed the code that disables it and recompiled it to run it and it doesn't work, so that means whatever changes that they made for it aren't in this code.