Similar to commit 94deed272 - " xwayland: Use sensible defaults for
rootful size", mark fullscreen mode as fixed so that the actual monitor
layout is not reflected in the single fullscreen rootful window.
Without this, if "-fullscreen" is used without "-geometry", the XRandR
configuration is taken from the compositor via wl_output/xdg-output and
cannot be changed by the X11 clients.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>