x11/libxkbcommon: Backport upstream patch for libxml2 2.14 compatibility with...

x11/libxkbcommon: Backport upstream patch for libxml2 2.14 compatibility with libxml 2.14+ and improve port

* Backport upstream commit d7e112febb7ab756563da6eced0a650396be5945
* Rework Makefile to closer follow Porters Handbook
  PORTVERSION --> DISTVERSION
  Move CPE_VENDOR, SHEBANG_FILES and USE_LDCONFIG to USES block
  Remove unused reference in MESON_ARGS

Reference:
https://github.com/xkbcommon/libxkbcommon/commit/d7e112febb7ab756563da6eced0a650396be5945

PR:		285910
Reviewed by:	manu
Approved by:	x11 (manu)