[cctbxbb] Removal of Boost.Thread support

[Jeffrey Van Voorst]

>> Another possibility is to use multiple processes/threads and communicate via
>> zeromq.  zmq is hyped alot, but ipython uses it for multiprocessing and
>> pyzmq is fairly easy to get on *nix platforms. I haven't checked into its
>> availability on MS Windows.
> It's not clear to me where this would actually make a difference -
> most of the code either isn't inherently parallel, or is so easily
> split up that we can use the multiprocessing module (or even a queuing
> system).  The direct summation is the only embarrassingly parallel
> routine that I'm aware of that's actually a huge bottleneck.
>
> -Nat
At a high level, the major benefit (of pyzmq over multiprocessing) would 
in instances where parts could be distributed among multiple machines or 
the process(es) are event-driven.  Therefore, the benefit is application 
dependent, and pyzmq would require installing and testing another 3rd 
party lib.

--Jeff