Fixes issue #684. (
Update: see !1100 (merged)
Fixes issue #684 (closed) Current implementation uses the same mutex (push_mutex) for data protection and notification from zmq (push_cond). Calling wait() method of push_cond unlocks push_mutex. Another thread could call push_event and corrupt data_call_cdr.
The proposed solution separates data protection and notification. It uses std::future and std::promise(c++11) for notification.
Edited by Nicolas Leclercq