We really don't *ever* want send to block, no matter how it is called,
since the send is always in the proxy thread. This makes the actual
send call always non-blocking, and adds callbacks that we can invoke on
send failures: either on queue full errors (which might be recoverable),
or both full queue and hard failures (which are generally not
recoverable). These callbacks are both optional: they have to be passed
in using `send_option::queue_full` (if you just want queue full
notifies) or `send_option::queue_failure` (if you want queue full
notifies *and* other send exceptions).
When we try to route an internal message ("BYE", "NOT_A_SERVICE_NODE",
etc.) back to the remote from the proxy thread we can end up trying to
send to a disconnected remote, which raises an exception, but this isn't
caught in proxy code: fix this by catching and ignoring it.
This also changes the code to send these messages in "dontwait" mode so
that if we can't queue the message we get (and ignore) an exception
rather than blocking.
lokimq.cpp and lokimq.h were getting monolithic; this splits lokimq.cpp
into multiple smaller cpp files by logical purpose for better parallel
compilation ability. It also splits up the lokimq.h header slightly by
moving the ConnectionID and Message types into their own headers.
Jason Rhinelander