[C++] deprecate overload resolution extension?

[dewar@gnat.com]

<<> However, I think we need some kind of unanimous consent before we
> proceed.  Another compromise would be to keep the code (which unlike
> some other extensions is simple, compartmentalized, well-documented,
> and safe), keep the !pedantic condition, but add a pedwarn.  That way
> pedantic users just get errors (instead of this rule kicking in, which
> they likely won't understand) and non-pedantic users get a warning.
>>

I think it's a bad idea not to flag this as an error. I am all in favor
of well conceived extensions that are permitted in non-pedantic mode,
but I just don't see this particular extension as well conceived, it
seems like a mistake to me, why perpetuate a mistake? The proper user
action is to disambiguate anyway, and I see no real downside in forcing
this desirable disambiguation.