Make it possible to recover from connect timeouts

Make it possible to recover from connect timeouts

Similarly to the read timeout, it's now possible to recover from
ISC_R_TIMEDOUT event by restarting the timer from the connect callback.

The change here also fixes platforms that missing the socket() options
to set the TCP connection timeout, by moving the timeout code into user
space.  On platforms that support setting the connect timeout via a
socket option, the timeout has been hardcoded to 2 minutes (the maximum
value of tcp-initial-timeout).