dix/randr: add a hooks into screen to (a) replace scanout pixmap and (b) for additional cursor confinement

 Backported from X.org:

 commit c41922940adbc8891575b3321fadf01ff4cb5854
 Author: Dave Airlie <airlied@redhat.com>
 Date:   Tue Jun 26 10:00:21 2012 +0100

    dix/randr: add a hook into screen to replace scanout pixmap

    For DRI2 in some offload cases we need to set a new pixmap on the crtc,
    this hook allows dri2 to call into randr to do the necessary work to set
    a pixmap as the scanout pixmap for the crtc the drawable is currently on.

    This is really only to be used for unredirected full screen apps in composited
    environments.
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

 commit e65c3f8bcc86845f21ac575e2bfb4b21b67d5ebf
 Author: Adam Jackson <ajax@redhat.com>
 Date:   Wed Jan 5 12:04:19 2011 -0500

    dix: Add a Screen method for additional cursor confinement

    This just reserves the slot in the ABI. Confining cursors to CRTCs will
    come soon.

    v2: Just reserve the slot.
Reviewed-by: Daniel Stone <daniel@fooishbar.org>
Signed-off-by: Adam Jackson <ajax@redhat.com>

 Backport to nx-libs: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>