Script arguments localhost:localport and remotehost:remoteport are now

Script arguments localhost:localport and remotehost:remoteport are now
optional, and default to `localhost' and ports 8025 and 25
respectively.

SMTPChannel.__init__(): Calculate __fqdn using socket.getfqdn()
instead of gethostby*() and friends.  This allows us to run this
script even if we don't have access to dns (assuming the localhost is
configured properly).

Also, restore my precious page breaks.  Hands off, oh Whitespace
Normalizer!