WIP: x11/gdm: Update to 41.3 (First draft)

[nc]

Summary

After being stuck on GDM 3.28 for a long time, here is a patch to update GDM
to 41.3. This brings GDM in line with the most of the other GNOME ports.

WHAT WORKS:

• Launching via X11
• Displaying a list of users
• Logging in

WHAT DOES NOT WORK:

• Unlocking the screen. It fails on this error:
  
  gdm 6526 - - GLib-GIO: g_dbus_connection_call_sync_internal: assertion 'object_path != NULL && g_variant_is_object_path (object_path)' failed gdm 6526 - - Gdm: Unable to determine if can activate sessions: gdm 6526 - - GLib: g_error_free: assertion 'error != NULL' failed
  
  This error is triggered by common/gdm-common.c in GDM. On GDM, it accepts a valid password but then goes back to the login screen.

Test Plan

Import this patch, rebuild GDM, and attempt to use it.

[nc]

Bugzilla report: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=261540

[nc]

Fix a small Makefile error. Sorry if GDM still doesn't work.

[nc]

Fix a path variable (sorry it still doesn't work :-( ).

[nc]

Fix another consolekit path.

[nc]

Good news! Got GDM working!