[C++] deprecate overload resolution extension?

[dewar@gnat.com]

<<We will be forcing the disambiguation; in the C++ frontend, pedwarns are
errors by default.  But I would like people to be able to build code that
relies on this with -fpermissive; again, I put this extension in because
things were breaking without it (though I don't remember what).
>>

Well that's not very convincing :-)

This "extension" clearly causes an ambiguous expression to be treated
as unambiguous by taking what is (in terms of the standard) an arbitrary
choice. 

Perhaps a convincing example would change people's minds. It seems like
any language extension should be thoroughly documented, with motivating
examples before it is implemented.