RFR: 8247908: Replace IsRegisteredEnum with std::is_enum

[Kim Barrett]

> On Jul 23, 2020, at 3:41 AM, David Holmes <david.holmes at oracle.com> wrote:
> 
> Looks good!

Thanks.

> 
> Thanks Kim!
> 
> David
> -----
> 
> On 23/07/2020 5:27 pm, Kim Barrett wrote:
>> Please review this change which removes our IsRegisteredEnum type
>> trait and its uses, instead using the std::is_enum<> type trait.
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8247908
>> Webrev:
>> https://cr.openjdk.java.net/~kbarrett/8247908/open.00/
>> Testing:
>> mach5 tier1