- Fixed several bugs with the async request socket.
   still not quite as reliable as I would like it. More improvements to come.
 - We now set high water marks to INT_MAX. Zeromq hides a little too much... Can't tell when it drops messages, and debugging is hard.
 - In the pollset: on some systems, boost::recursive_lock may never get the lock when contended. Particularly because the poll
   thread is basically busy looping around the mutex. The implementation in boost 1.50 does not appear to be "fair".
   Added a "contention" flag to help move give the mutex away when contended.