option_map: Diagnose unused option on request

* spot/misc/optionmap.hh, spot/misc/optionmap.cc (report_unused_options,
set_, set_set_): New methods.
* bin/autfilt.cc, bin/dstar2tgba.cc, bin/ltl2tgba.cc,
bin/ltl2tgta.cc: Call report_unused_options().
* tests/core/ltlcross2.test, tests/core/readsave.test: Fix typos in
options.
* tests/core/minusx.test: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention this.

tests/core/minusx.test

@@ -0,0 +1,30 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2016 Laboratoire de Recherche et Développement de
+# l'Epita (LRDE).
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Spot is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. ./defs
+set -e
+
+# make sure option -x reports unknown arguments
+ltl2tgba -F- -x foo </dev/null 2>error && exit 1
+grep "ltl2tgba: option 'foo' was not used" error
+ltl2tgba -F- -x ba-simul,foo,bar </dev/null 2>error && exit 1
+grep -v 'ba-simul' error
+grep -- "- 'foo'" error
+grep -- "- 'bar'" error