autfilt add support for --partial-degeneralize

* bin/autfilt.cc: Add a --partial-degeneralize option.
* NEWS: Mention it.
* spot/twaalgos/degen.cc: Do not restrict partial_degeneralize() to
deterministic automata.
* spot/twaalgos/degen.hh: Adjust documentation.
* tests/core/pdegen.test: New test case.
* tests/Makefile.am: Add it.
* tests/python/pdegen.py: Adjust.

tests/core/pdegen.test

@@ -0,0 +1,32 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2020 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
+
+randaut -n10 -e.3 -Q7 -A 'generalized-co-Buchi 2..5' 2 |
+  autcross --verbose --language-preserved \
+      'autfilt --partial-degen' \
+      'autfilt --partial-degen=1,2,3'
+
+randaut -n10 -e.3 -Q7 -A 'random 2..5' 2 |
+  autcross --verbose --language-preserved 'autfilt --partial-degen'