G++ enums 'underlying type'

[Paolo Carlini]

Gabriel Dos Reis wrote:

>All that is moot; for to properly implement at the traits at issue
>(is_enum), one needs hooks in the compiler.
>
I think that what we already have is rather good, overall, and doesn't need
by itself hooks of any kind.

The only problem is caused, as a secondary effect, by a *bug*, or, 
better said,
unimplemented ISO feature, of the compiler, that is, c++/19076. For 4.0, I
will provide a work-around for that issue (similarly to Boost).

Paolo.