Ensure termination of threads
Ensure termination of threads

Make sure there's no point where a callback is waiting indefinitely on a
lock; i.e. that any processing can be terminated by some means. Also
enhanced the MMALBuffer repr to include the command/event and brought
MMALPythonConnection into line with MMALConnection's behaviour when
disabled: leave the connected components enabled and just disable the
connected ports.

tfroehlich82/picamera,waveform80/picamera