To enable ConsoleKit in a graphical session, prepend ck-launch-session
to the session script (note: gdm(1) does this automatically). e.g.
    /usr/local/bin/ck-launch-session /usr/local/bin/bin/xfce4-session

The /var/log/ConsoleKit/history logfile can grow very large after some
time. It is advised to use newsyslog(8) to rotate it.
