RFR: 8273924: ArrayIndexOutOfBoundsException thrown in java.util.JapaneseImperialCalendar.add()

[Naoto Sato]

Fixing an AIOOBE on normalizing the month value.

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Commit messages:
 - 8273924: ArrayIndexOutOfBoundsException thrown in java.util.JapaneseImperialCalendar.add()

Changes: https://git.openjdk.java.net/jdk/pull/5611/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5611&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273924
  Stats: 26 lines in 3 files changed: 24 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5611.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5611/head:pull/5611

PR: https://git.openjdk.java.net/jdk/pull/5611