ggm@apnic.net said:
> I'm keeping current by doing: 
> [...]
> 	# (cd /usr/obj/destdir.i386; tar cBPf - .) | tar --unlink -xBpf -

So anything in the working system stays there.
Normally, there is the "obsolete" mechanism which takes care of
old files, but since gcc3 is not yet in the standard distribution
lists, this wouldn't help.
You really have to clean out /usr/include/g++ in the final target tree
(not your temporary DESTDIR) manually.

> So I guess that left some crap around, which while not referenced internally in
> the /usr/include hierarchy, was detected by ./configure processes and so caused
> it to make a bad config.h -Is that it?

I'm not sure "configure" is involved here.

> > split.cpp:13: error: no match for 'operator>>' in 's >> item'/usr/
> > include/g++/iostream.h:200: error: candidates are: istream&
> > istream::operator>>(char*) 

/usr/include/g++/iostream.h shouldn't be there.

best regards
Matthias