gdm pam changes

[Ray Strode <halfline gmail com>]

Hey guys,

GDM no longer hardcodes consolekit registration logic in it anymore.
For distributions that use consolekit, it now depends on
pam_ck_connector for that registration in just the same way
distributions that use pam_systemd do for systemd integration.

The fix is fairly straight forward, in each of gdm's pam files (or
files included by gdm's pam files, such as system-auth), put

-session optional pam_ck_connector.so

This can go in the same place as the systemd line for distros trying
to support both at the same time.

--Ray