Degraded C++ error messages

[Paolo Carlini]

> There's always STLfilt, which does this sort of thing in a post-processing 
> step. I'm surprised it hasn't yet been mentioned:

I didn't since, due to network issue on my side, I didn't actually read you
message! ;)

Anyway, I'd like to mention that this kind of tool, which I like a lot, since
has to deal via regular expression matching with the *mutable* internal details
of the library (that, as we know well, unfortunately show up in the unfiltered
error messages!) is *very* fragile, and needs **continuos** maintainance!!!

For instance, I think that if you try the latest version on current v3 you
may notice that is not able to filter well stupid errors like:

	std::list<int> v;
	std::stable_sort(v.begin(), v.end());

Paolo.