RFR: Refresh libclang (take three)

[Maurizio Cimadamore]

This PR brings the libclang generated sources in sync with the latest jextract changes.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/jextract/pull/202/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=202&range=00
  Stats: 3950 lines in 9 files changed: 2720 ins; 373 del; 857 mod
  Patch: https://git.openjdk.org/jextract/pull/202.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/202/head:pull/202

PR: https://git.openjdk.org/jextract/pull/202