Review needed for the EnumSet template

[Enamex via Digitalmars-d]

On Thursday, 3 September 2015 at 00:12:06 UTC, BBasile wrote:
> Memebers should be notified.
>
> https://github.com/D-Programming-Language/phobos/pull/3623
>
> It's not a big stuff but it's neither a small addition.
> The thing is there.

Slightly tangential question: in your "superset" enumset package, 
what's the use of 'static' annotation on a free function (was the 
first function I saw in the file, I believe)?