[jfx11u] Integrated: 8286256: Update libxml2 to 2.9.14

[Kevin Rushforth]

Clean backport to `jfx11u`.

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

Commit messages:
 - 8286256: Update libxml2 to 2.9.14

Changes: https://git.openjdk.java.net/jfx11u/pull/101/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=101&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286256
  Stats: 21664 lines in 81 files changed: 4429 ins; 4294 del; 12941 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/101.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/101/head:pull/101

PR: https://git.openjdk.java.net/jfx11u/pull/101