On unix we don't safe much (otherwise csync would have been
designed differently).
On windows however, the readdir already fetch all the info, so we
can as well use it.
We still have to query for the file id but we might optimize that later
Before we only had c_utf8_to_locale, but now functionality is needed to
convert a path to UNC before converting it. That does c_utf8_path_to_locale
now, while c_utf8_string_to_locale only converts the plain string, ie.
to generate wide char strings for output.
