Use EV_DEFAULT_UC_ instead of EV_DEFAULT_

ev_default_loop() is already called unconditionally quite early in
main(), so we always have a default loop. The _UC variant avoids some
checks and should therefore generate insignificantly smaller code and
should also be insignificantly faster. It's the insignificant
improvements that count! *cough*

At least there is some consistency now.
main.c: Init the hub manager before dispatching and entering main loop

I wonder why I did it the other way around before.
hub/connection: Add a timeout on clean disconnect

There's no point in waiting too long for a clean disconnect to complete.
In fact, it may be harmful if the connection is bad because it may
indefinitely stall a reconnect.