[foreign-jextract] RFR: 8252247: regenerate jdk.internal.clang.libclang sources using jextract

[Athijegannathan Sundararajan]

Regenerated libclang classes and manually adjusted as documented.

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Commit messages:
 - 8252247: regenerate jdk.internal.clang.libclang sources using jextract

Changes: https://git.openjdk.java.net/panama-foreign/pull/290/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/290/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252247
  Stats: 20556 lines in 14 files changed: 13914 ins; 5718 del; 924 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/290.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/290/head:pull/290

PR: https://git.openjdk.java.net/panama-foreign/pull/290