x11-wm/xfce4-session default reboot/halt/suspend permissions

[J.R. Oldroyd]

Hi folks,

Port x11-wm/xfce4-session currently provides a pkg-message that advises
folk to add a .pkla file in:
    %%LOCALBASE%%/etc/polkit-1/localauthority/50-local.d
that adds the necessary PolicyKit permissions to add reboot/halt and
now also suspend capabilities to the xfce4-session-logout dialog.

It requires users to copy a sample, and edit:
    Identity=unix-group:PUTYOURGROUPHERE

I would like to propose that this file be installed by the port with
the above line set to:
    Identity=unix-group:wheel

My intent here is to automatically enable reboot/halt/suspend capability
in a way that doesn't open new holes.  Users in group wheel can already
reboot/halt/suspend, so this will work as expected on systems with users
in the wheel group.  Users in other groups can still edit the file as
they need.

Any problems with this?

	-jr