error message formatting

[Joe Buck]

> To be concrete, I think if we check to see if the type of a template
> parameter is the default value for the parameter, it be not printed
> if it would have been the last one printed.

Yes, this is what I proposed (presumably egcs list delays mean we didn't
see each other's postings until later).  This one would be fairly
straightforward and shouldn't cause problems.

> Also, if there exists a typedef name for a type, then we use the
> typedef name instead of the real name, if the real name is a template
> of some kind.

This one, on the other hand, may be trickier, because there are often
multiple typedefs referring to the same type (especially for maps and
sets: there is the map iterator as well as the rb_tree iterator).  It
might be tricky to decide which one to choose for display.