Upgrade (almost) to natd 2.0b1

Upgrade (almost) to natd 2.0b1

  - Transparent proxy support.
  - PERMANENT_LINK IS NOW OBSOLETE, use redirect_port instead.
  - Drop support for early FreeBSD 2.2 versions
  - If separate input & output sockets are being used
    use them to find out packet direction instead of
    normal mechanism. This can be handy in complex environments
    with multiple interfaces.
  - PPTP redirect support by Dru Nelson <dnelson@redwoodsoft.com> added.
  - Logging enhancements from Martin Machacek <mm@i.cz> added.

Obtained from: Ari Suutari <ari@suutari.iki.fi>