Previous commit 3c883c4b31 added support
for parsing option -- in particular -c/--config -- and added some way of
detecting invalid arguments. But the detection was incorrect.
getopt will stop looking for arguments when it detects a non-argument
(dash-prefixed) which is not an option parameter, but checking that
options were all consumed should be done right after by comparing the
options up to this last non-argument and those that were detected.
This only displays the first unrecognized option, mimicking the
behaviour of most software.
9b2ffafd93