[foreign-jextract] Integrated: 8262825: jextract crashes when Java type names like String are used as identifiers in C header

[Athijegannathan Sundararajan]

Unqualified Java type names used in generated code are mangled (like keywords, restricted type names)

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Commit messages:
 - 8262825: jextract crashes when Java type names like String are used as identifiers in C header

Changes: https://git.openjdk.java.net/panama-foreign/pull/463/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=463&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262825
  Stats: 115 lines in 4 files changed: 112 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/463.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/463/head:pull/463

PR: https://git.openjdk.java.net/panama-foreign/pull/463