screen: Remove no-op statement

This was at one time necessary to create the cursor tracker, but
now that it's global we don't need it anymore.
cursor-renderer: Remove the MetaScreen

It's unused.
cursor-tracker: Improve symmetry between two paths
Move the cursor renderer to the backend
wayland: Remove the stage destroy hook

We assert fail / segfault when pressing the "X" button anyway, so
I don't think it does us too much good.
compositor: Create the MetaWaylandStage here
cursor-renderer: Kill a warning

This can happen during early initialization. We should have a
better initialization plan.
wayland: Kill extra includes to meta-wayland-stage.h

No idea why these are still included at all...
Rename MetaWaylandStage to MetaStage and put in compositor/
Move the painting of the cursor on the stage out of the cursor renderer

This logic is now well-contained the stage. This is the start of us
moving to backend-specific cursor renderers.
cursor: Retrieve the GBM device from the MetaBackend

Not the MetaCursorTracker.
weston-launch: Go through the MetaBackend to force-update the cursor
cursor-renderer: Fix HW cursors

We need to make sure that we update the HW cursor if we disable
it for some reason.
cursor-renderer: Rewrite HW cursors to be cleaner
backends: Add a native cursor renderer