GNOME version of xdm display manager

- This port doesn't work on the normal FreeBSD 3.x-RELEASEs because
  those pam is not stable.
  I'm sure this works on 5.0-current, and it may works on 4.x-RELEASE

  You should append those lines to your /etc/pam.conf

# gdm config
gdm     auth            requisite       pam_unix.so     try_first_pass
gdm     account         requisite       pam_unix.so     try_first_pass
gdm     session         required        pam_permit.so

This notes is written by:  Yukihiro Nakai <nakai@FreeBSD.org>