How about adding a few more names from the std namespace to get appropriate
hints?  This patch compiles and the appropriate messages are printed.  Is
there a problem with just adding more or even at some point all the symbols
of the standard library?

gcc/ChangeLog:

        * cp/name-lookup.cc (get_std_name_hint): Add more symbols from the
        <iomanip>, <ios>, <istream> and <ostream> headers.