If you run weston with the headless backend, you get a Wayland
display with no seat, which is just fine by the protocol.
gdk_display_get_default_seat() returns NULL in this case. Various
widgets assume that we always have a seat with a keyboard and a
pointer, since that is what X guarantees. Make things survive
without that, so we can run the testsuite under a headless
Wayland compositor.
The calls used old bugzilla URLs and nobody cared about that.
So apparently they are very unused.
There's also a potential conflict between gitlab and bugzilla URLs and
what base bug to use there.
The old usages have been converted to comments.
