Integrated: 8310686: [lw5] check that only value classes with implicit constructor can implement NonAtomic

[Vicente Romero]

check that only value classes with implicit constructor can implement NonAtomic

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Commit messages:
 - 8310686: check that only value classes with implicit constructor can implement NonAtomic

Changes: https://git.openjdk.org/valhalla/pull/873/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=873&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310686
  Stats: 12 lines in 2 files changed: 12 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/873.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/873/head:pull/873

PR: https://git.openjdk.org/valhalla/pull/873