scc_filter: preserve state names and highlighted states

Suggested by Juraj Major.

* spot/twaalgos/sccfilter.cc: Here.
* tests/python/sccfilter.py: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the news.

tests/python/sccfilter.py

@@ -0,0 +1,60 @@
+#!/usr/bin/python3
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2016 Laboratoire de Recherche et Développement de
+# l'EPITA.
+#
+# 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/>.
+
+# Make sure scc_filter preserves state-names (suggested by Juraj
+# Major)
+
+import spot
+
+a = spot.automaton("""
+HOA: v1.1
+States: 3
+Start: 1
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+spot.highlight.states: 0 0 2 3
+--BODY--
+State: 0 "baz"
+[t] 0
+State: 2 "foo" {0}
+[0] 0
+[0] 2
+[!0] 2
+State: 1 "bar"
+[0] 2
+--END--
+""")
+
+assert (spot.scc_filter(a, True).to_str('hoa', '1.1') == """HOA: v1.1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc !complete
+properties: deterministic
+spot.highlight.states: 1 3
+--BODY--
+State: 0 "bar"
+[0] 1
+State: 1 "foo" {0}
+[t] 1
+--END--""")