[jdk17u-dev] RFR: 8339803: Acknowledge case insensitive unambiguous keywords in tzdata files

[Goetz Lindenmaier]

I backport this for parity with 17.0.14-oracle.

Clean backport from 21.

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Commit messages:
 - Backport f4940f65f8908602e2043caaf1141150be865acc

Changes: https://git.openjdk.org/jdk17u-dev/pull/3028/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3028&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339803
  Stats: 20 lines in 3 files changed: 4 ins; 0 del; 16 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3028.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3028/head:pull/3028

PR: https://git.openjdk.org/jdk17u-dev/pull/3028