Getting Apple's libstdc++ debug mode into the FSF tree

[Benjamin Kosnik]

>Actually I meant what Benjamin suggested, i.e. -debug=c++.

For the record, I don't think I actually came up with this but I do like
it and think it makes the most sense, so I've been talking it up. I
think it was either Loren or Gaby, but I really have no idea.

;)

It seem as if there is consensus on using -debug=c++ among a wide
variety of people, so if there's another iteration of this patch,
perhaps this should be used.

-benjamin