RFR: 8286294 : ForkJoinPool.commonPool().close() spins [v3]

[Doug Lea]

> Changes ForkJoinPool.close spec and code to trap close as a no-op if called on common pool

Doug Lea has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8286294
 - Fix doc types
 - Override close as explicit no-op for common pool

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8577/files
  - new: https://git.openjdk.java.net/jdk/pull/8577/files/5ceb0794..c276385c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8577&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8577&range=01-02

  Stats: 103528 lines in 1259 files changed: 93903 ins; 4285 del; 5340 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8577.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8577/head:pull/8577

PR: https://git.openjdk.java.net/jdk/pull/8577