only dme.xml knows that it should use the selected nav[0] frequency with

only dme.xml knows that it should use the selected nav[0] frequency with
switch-position=1, so let's set it here for all others. This shouldn't be
done in aircraft *-set.xml files (unless there's a *very* good reason),
because this overwrites the settings that were made by the --dme option,
and thus breaks it.