RFR: 8292458: Atomic operations on scoped enums don't build with clang [v3]

[Kim Barrett]

> Please review this change to allow the Atomic class to support scoped enum
> values on all platforms.  We do this by adding PrimitiveConversions::Translate
> support for enums (converting to/from the underlying type), and changing
> relevant Atomic operations to use that translation instead of trying to handle
> enums on the integer code path.
> 
> Testing:
> mach5 tier1-3, including gtests added by this change

Kim Barrett 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 four additional commits since the last revision:

 - Merge branch 'master' into atomic-enum
 - use _t suffixed type traits
 - atomic ops use new enum translator
 - test atomics on enums

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9895/files
  - new: https://git.openjdk.org/jdk/pull/9895/files/33e1c850..8d9769ed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9895&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9895&range=01-02

  Stats: 37977 lines in 258 files changed: 16689 ins; 19762 del; 1526 mod
  Patch: https://git.openjdk.org/jdk/pull/9895.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9895/head:pull/9895

PR: https://git.openjdk.org/jdk/pull/9895