Backported from X.org:

   commit 16381d186e7c791031392ed8afcfd33009854e9e
   Author: Giuseppe Bilotta giuseppe.bilotta@gmail.com
   Date: Thu Nov 9 10:21:20 2017 +0100

   randr: always realloc crtcs and outputs

   When the last crtc (resp. output) is destroyed, the rrScrPriv crtcs
   (resp. outputs) fields do not get cleared, which can lead to a situation
   where the private's numCrtcs (resp. numOutputs) field is zero, but the
   associated memory is still allocated. Just checking if numCrtcs (resp.
   numOutputs) is zero is thus not a good criteria to determine whetehr to
   use a realloc or a malloc.

   Since crtcs (resp. outputs) are NULL-initialized anyway, relying on
   numCrtcs (resp. numOutputs) is actually unnecessary, because
   reallocation of a NULL ptr is equivalent to a malloc anyway.

   Therefore, just use realloc() unconditionally, and ensure that the
   fields are properly initialized.
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Fixes ArcticaProject/nx-libs#558