Roman Gilg authored Mar 13, 2018 and Adam Jackson committed Mar 28, 2018

In contrast to screen flip mode this mode:
* supports flips per windows (these windows currently need to have the same
  size as their parent windows with the same pixmap),
* sends pixmap idle signals to the client only after the driver has given
  an additional event notify.

This patch only introduces the new mode as a stub. It additionally needs a
driver hook, such that it can get initialized and appropriate cleanup
functions.

Signed-off-by: Roman Gilg <subdiff@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>