dix: add missing include for DeleteWindowFromAnySelections

Fixes build error with XACE disabled:
window.c:886:5: error: implicit declaration of function 'DeleteWindowFromAnySelections' [-Werror=implicit-function-declaration]
     DeleteWindowFromAnySelections(pWin);
     ^

Debian bug#701372

Reported-by: Matthias Klose <doko@debian.org>
Signed-off-by: Julien Cristau <jcristau@debian.org>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Keith Packard <keithp@keithp.com>