libX11: update to 1.8.3.

This bug fix release corrects some regressions introduced in 1.8.2
along with other bugs.

Highlights include:

* Improved handling of reentering libX11 via X*IfEvent() calls (!171, !173)
* Fix loading of en_US.UTF-8/XLC_LOCALE (#167, !174)
* Add XFreeThreads() and automatic call from a destructor function when
  thread-safety-constructor is enabled (!167).
* Address issues found by UBSan and AddressSanitizer
* Fix build with older gcc versions (!169)

The full list of changes - see https://gitlab.freedesktop.org/xorg/lib/libx11/
for further details on any of these:

Alan Coopersmith (1):
      libX11 1.8.3

Jeremy Huddleston Sequoia (1):
      ximcp: Address warning found by UBSan when growing an empty tree

Keith Packard (1):
      Update XPutBackEvent() to support clients that put back unpadded events

Matthieu Herrb (1):
      Fix 797755 Allow X*IfEvent() to reenter libX11

Nia Alarie (1):
      Don't use pragma inside a function, it breaks compiling with older GCCs.

Oliver (1):
      Add XFreeThreads function.

Takao Fujiwara (1):
      nls: consecutive cs number in en_US.UTF-8/XLC_LOCALE

Ulrich Sibiller (2):
      Indentation fixes around recent dpy->in_ifevent changes
      ChkIfEv.c: fix wrong handling of dpy->in_ifevent

(wiz)