Backported from X.org:

 commit e7fae9ecc42ab5e73b89117722dbf4117d928f9a
 Author: Jamey Sharp <jamey@minilop.net>
 Date:   Sat May 22 00:26:28 2010 -0700

    Move each screen's root-window pointer into ScreenRec.

    Many references to the WindowTable array already had the corresponding
    screen pointer handy, which meant they usually looked like
    "WindowTable[pScreen->myNum]". Adding a field to ScreenRec instead of
    keeping this information in a parallel array simplifies those
    expressions, and eliminates a MAXSCREENS-sized array.

    Since dix uses this data, a screen private entry isn't appropriate.

    xf86-video-dummy currently uses WindowTable, so it needs to be updated
    to reflect this change.
Signed-off-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Tiago Vignatti <tiago.vignatti@nokia.com>
    Tested-by: Tiago Vignatti <tiago.vignatti@nokia.com> (i686 GNU/Linux)

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