[fs.dir.entry.io]
31 Input/output library [input.output]
31.12 File systems [filesystems]
31.12.10 Class directory_entry [fs.class.directory.entry]
31.12.10.5 Inserter [fs.dir.entry.io]
template<class charT, class traits>
friend basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const directory_entry& d);