xserver-xorg: upgrade 21.1.6 -> 21.1.18

xserver-xorg: upgrade 21.1.6 -> 21.1.18

xorg-server 21.1.17
This release contains the fixes for the issues reported in today's security
advisory: https://lists.x.org/archives/xorg/2025-June/062055.html

   * CVE-2025-49175
   * CVE-2025-49176
   * CVE-2025-49177
   * CVE-2025-49178
   * CVE-2025-49179
   * CVE-2025-49180

Additionally, this release includes a fix for CVE-2022-49737 which was
issued after the fix was merged back in 2022 and several other various fixes.

Ref: https://lists.x.org/archives/xorg-announce/2025-June/003609.html

xorg-server 21.1.18
This release contains an additional fix for CVE-2025-49176 from June 17
security advisory: https://lists.x.org/archives/xorg/2025-June/062055.html

Ref: https://lists.x.org/archives/xorg-announce/2025-June/003612.html

Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a59b385184fb3a548dc27310fd04d64351d8dfba)
Signed-off-by: Steve Sakoman <steve@sakoman.com>