- Ideally Queues must outlive the threads using them, but wasn't done so. Yes, std::shared_ptr them!
- Now queues are always valid in the context of the threads using them.
- No longer need tedious queues deallocation by the original owner.
- Misc cleanups.
Besides deadlocks, a thread can in theory get stuck in a blocking pop(),
not seeing the stopping flag in particular. So assure liveness by making all
pop() timed pop.
Removed the NotifyQueue between DemodulatorInstance participants, actually not needed
since DemodulatorInstance::IsTerminated() is explicitly called on some events for cleanups
DELETE_CLEANUP: properly nullify deleted pointers when needed