New AIX regressions

[Benjamin Kosnik]

How about just this

> 2002-04-29  Benjamin Kosnik  <bkoz@redhat.com>
> 
>         PR libstdc++/5820
>         * include/bits/fstream.tcc
>         (basic_filebuf::_M_underflow_common): Check for eof.
>         * include/bits/streambuf_iterator.h: Match stream_iterator.h.
>         (istreambuf_iterator::operator++): Invalidate on eof.
>         (istreambuf_iterator::operator++(int)): Same.
>         (istreambuf_iterator::operator*): Same.