Crash on exit

[Stivius]

Describe the bug
Player crashes on exit sometimes.

To Reproduce

• Launch the player
• Close the player window (not ^C in terminal)

Expected behavior
No crash.

Logs
It gives the following message:
Invalid argument (/root/zeromq-4.3.0/src/mutex.hpp:142) Aborted (core dumped)

Environment (please complete the following information):

• Linux Disto: Manjaro 18.0.4
• Linux Desktop Environment: XFCE
• How the player was launched: snap
• Player Version: 1.8-R2

[Stivius]

This issue was due to an internal error in zeromq 4.3.0. I've found the discussion here: zeromq/libzmq#2991

Apart from that, I've decided to remove cppzmq because these bindings are updated much slower than the original library. Moreover, they use custom versioning that doesn't conform to the original lib versioning.

Also, termination wasn't done correctly before. According to ZMQ docs, zmq::context should be terminated only after all zmq::socket have been closed. Now we have 3-steps termination:

• shutdown any blocking operation on zmq::socket thread
• join zmq::socket thread
• and now we can safely call terminate function to destroy and free context resource