RFR: 8292458: Atomic operations on scoped enums don't build with clang [v2]

[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 incrementally with one additional commit since the last revision:

  use _t suffixed type traits

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9895/files
  - new: https://git.openjdk.org/jdk/pull/9895/files/664326b8..33e1c850

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9895&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9895&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 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