[Bug c/71199] Support overloadable attribute in GNU C front-end

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71199

--- Comment #9 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
(In reply to Yu Xuanchi from comment #6)
> So I think in short term. We just reject those code. Because our aim is to
> support this feature like clang. If there is no any problem. I'll go impl it.

Agreed, we really don't care about this nested case, so rejecting it as Clang
does seems appropriate to me.