[jfx17u] RFR: 8286256: Update libxml2 to 2.9.14

[Kevin Rushforth]

Clean backport to `jfx17u`.

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Commit messages:
 - 8286256: Update libxml2 to 2.9.14

Changes: https://git.openjdk.java.net/jfx17u/pull/61/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx17u&pr=61&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/jfx17u/pull/61.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx17u pull/61/head:pull/61

PR: https://git.openjdk.java.net/jfx17u/pull/61