Use of strings in new exception implementation (report libstdc++/1972)

[Greg Bumgardner]

Do you think you'll be revisiting that code in the near future?

If you would like, I can take a swing at fixing the exceptions so they
properly copy the value of the string argument. I'm thinking that it would
be best to strdup the value of c_str() and store that in the two concrete
exceptions, so we can continue to use stringfwd for the interface.

What do you say?

I'm also curious about the handling of assignment operators.  The standard
shows that exception has an assignment operator, even though it has nothing
to assign, but none of the derived classes have them.  If we don't design
these classes to correctly support assignment, then the operator should
probably be declared private.

-g.b.