merge xorg-serer 21.1.3.

Backport the only patch from xorg-server 1.20.9 as I can't find a tarball.

From aac28e162e5108510065ad4c323affd6deffd816 Mon Sep 17 00:00:00 2001
From: Matthieu Herrb <matthieu@herrb.eu>
Date: Sat, 25 Jul 2020 19:33:50 +0200
Subject: [PATCH] fix for ZDI-11426

Avoid leaking un-initalized memory to clients by zeroing the
whole pixmap on initial allocation.

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative

Signed-off-by: Matthieu Herrb <matthieu@herrb.eu>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>

initial import of xorg-server-1.20.6

initial import of xorg-server-1.20.3

initial import of xorg-server-1.18.4

import xorg-server 1.9.2. important changes since 1.6.5 include:

- built-in symbol visibility, default not export
- fixes for various crashes
- many fixes for XI2, EXA, dix, render, glx, xkb, EDID, randr, Xv,
resource handling, Xext, vfb, xfree86 / vga and composite support.
- fixes several memory leaks
- many many documentation updates
- record extension enabled
- no longer looks for XF86Config files

initial import of xorg-server-1.6.1.901

initial import of xorg-server-1.4.2