RFR: 8286294 : ForkJoinPool.commonPool().close() spins [v4]

[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 incrementally with three additional commits since the last revision:

 - Accommodate restrictive SecurityManagers
 - merge with loom updates
   Merge remote-tracking branch 'refs/remotes/origin/JDK-8286294' into JDK-8286294
 - Fix testLazySubmit; enable suite

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8577/files
  - new: https://git.openjdk.java.net/jdk/pull/8577/files/c276385c..9a0d27f4

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8577&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8577&range=02-03

  Stats: 21 lines in 1 file changed: 12 ins; 4 del; 5 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