RFR: 7903148: jextract crashes when C11 keyword _Static_Assert is used in a header

[Athijegannathan Sundararajan]

Added missing CursorKind enum value.

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Commit messages:
 - _Static_Assert -> _Static_assert in comments.
 - 7903148: jextract crashes when C11 keyword _Static_Assert is used in a header

Changes: https://git.openjdk.java.net/jextract/pull/15/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jextract&pr=15&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903148
  Stats: 69 lines in 4 files changed: 65 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jextract/pull/15.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/15/head:pull/15

PR: https://git.openjdk.java.net/jextract/pull/15