RFR: JDK-8296743: Tighten Class.getModifiers spec for array classes [v3]

[Joe Darcy]

> Update the spec of Class.getModifiers to match long-standing behavior for primitive and array classes. Remove unneeded implementation flexibility with regard to setting other bit positions. This work was prompted to better support anticipated future Valhalla changes.
> 
> Please also review the CSR: https://bugs.openjdk.org/browse/JDK-8297237

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Respond to review feedback.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11229/files
  - new: https://git.openjdk.org/jdk/pull/11229/files/dd1f3005..375c260d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11229&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11229&range=01-02

  Stats: 29 lines in 2 files changed: 2 ins; 9 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/11229.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11229/head:pull/11229

PR: https://git.openjdk.org/jdk/pull/11229