unknown arguments instead of erroring out.  This doesn&#8217;t
work for all combinations of arguments as users might expect
it to do.  E.g. if the first argument in <code>--unknown --known</code>
takes a value (which we can&#8217;t know), the second one is
mistakenly interpreted as a known option.  Similarly, if
<code>PARSE_OPT_STOP_AT_NON_OPTION</code> is set, the second argument in
<code>--unknown value</code> will be mistakenly interpreted as a
non-option, not as a value belonging to the unknown option,
