#4 Don't crash when server not available.

[Wes Peters]

I used IMAPAssassin to filter a hosted email account across the
wild wild Internet. Often after pausing for a few minutes,
IMAPAssassin cannot reconnect to the mail server, crashing on the
select after the failed connect on line 121.

This patch fixes the patch and implements a simple scalable
backoff if the server is not available. I've kept IMAPAssassin
running for as long as 25 days with this patch.

IMAPAssassin works great on FreeBSD, by the way. I'm running
on FreeBSD-current.

[Wes Peters]

Patch to handle server not available on reconnect