Queues and dispatchers are now strongly associated with a thread.

- Dispatchers can now detect if they're dispatching on the wrong thread.
- Publishers can now detect if they're dispatching to a thread.
  This may not work correctly in the case where the actual sub is
queuing to another thread.
Small cosmetic change in demux.hpp.
Bashed some most vexing parses in main inits.
Added unsubscribe() to scoped_subscription_c.
Added basic mech for event crackers, crackers for publisher events.
Greatly simplified how crackers are specified.

They are basically the same as demux, except that it takes an ostream
param and a const ref rather than const sp.
Merge branch 'master' of github.com:fsecilia/mmc