RFR: 8352162: Update libxml2 to 2.13.6 [v4]

[Jay Bhaskar]

> The upgrade is required to address several known issues from the previous version to improve stability and performance.

Jay Bhaskar has updated the pull request incrementally with one additional commit since the last revision:

  remove libxml2.rc

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/1785/files
  - new: https://git.openjdk.org/jfx/pull/1785/files/19ede147..1ea01cc1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1785&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1785&range=02-03

  Stats: 36 lines in 1 file changed: 0 ins; 36 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1785.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1785/head:pull/1785

PR: https://git.openjdk.org/jfx/pull/1785