introduce spot::split_edges()

Fixes #255.

* spot/twaalgos/split.cc, spot/twaalgos/split.hh,
tests/core/split.test: New files.
* spot/twaalgos/Makefile.am, tests/Makefile.am: Add them.
* bin/autfilt.cc (--split-edges): New option.
* python/spot/impl.i: Process split.hh.
* tests/python/alternating.py: Test split_edges() on
an alternating automaton.

tests/core/split.test

@@ -0,0 +1,29 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2017 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
+
+test 3,7 = `ltl2tgba 'a U b' --stats=%e,%t`
+test 7,7 = `ltl2tgba 'a U b' | autfilt --split --stats=%e,%t`
+test 12,12 = `ltl2tgba 'a U b' | autfilt -C --split --stats=%e,%t`
+test 0,0 = `ltl2tgba 0 | autfilt --split --stats=%e,%t`
+test 1,1 = `ltl2tgba 0 | autfilt -C --split --stats=%e,%t`