x11/libX11: Update to 1.7.1.
https://lists.x.org/archives/xorg-announce/2021-May/003088.html
https://lists.x.org/archives/xorg-announce/2021-May/003089.html
PR: 256034
Security: CVE-2021-31535
(cherry picked from commit 275cdd9b5f5b66999dc8bcafa610eaa85b5b7b55)