randr: Add "RANDR Emulation" property

When RANDR is emulated as with Xwayland, the actual output configuration
does not change as RANDR is emulated using viewports.

As a result, changes to the CRTC may be skipped, resulting in the
configuration being (wrongly) assumed to be unchanged.

Add a new output property "RANDR Emulation" that the DDX can set to
force RRCrtcSet() to reconfigure the CRTC regardless of the change.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>