postproc: add the possibility to output a monitor

* src/tgbaalgos/stripacc.cc, src/tgbaalgos/stripacc.hh: New files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbaalgos/postproc.cc, src/tgbaalgos/postproc.hh: Add a Monitor
output option.
* src/bin/ltl2tgba.cc: Add a --monitor/-M option.
* NEWS: Mention monitors.
* src/tgba/tgbaexplicit.hh (is_accepting_state): Fix for the
case where the automaton has no acceptance set.

src/tgbaalgos/stripacc.hh

@@ -0,0 +1,34 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2012 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/>.
+
+#ifndef SPOT_TGBAALGOS_STRIPACC_HH
+# define SPOT_TGBAALGOS_STRIPACC_HH
+
+# include "tgba/tgbaexplicit.hh"
+
+namespace spot
+{
+  /// \brief Duplicate automaton \a a, removing all acceptance sets.
+  ///
+  /// This is equivalent to marking all states/transitions as accepting.
+  /// \ingroup tgba_misc
+  sba_explicit_number* strip_acceptance(const tgba* a);
+}
+
+#endif // SPOT_TGBAALGOS_STRIPACC_HH