Disable IOCP and retry event_base_new_with_config once on failure

Disable IOCP and retry event_base_new_with_config once on failure

This is a fancier bug4457 workaround for 0.2.3.  In 0.2.2, we could
just tell Libevent "Don't enable locking!" so it wouldn't try to make
the event_base notifiable.  But for IOCP, we need a notifiable base.
(Eventually, we'll want a notifiable base for other stuff, like
multithreaded crypto.)  So the solution is to try a full-featured
initialization, and then retry with all the options turned off if that
fails.