postproc: add support for co-Büchi output

* spot/twaalgos/cobuchi.cc, spot/twaalgos/cobuchi.hh (to_nca): New
function.
(weak_to_cobuchi): New internal function, used in to_nca and to_dca
when appropriate.
* spot/twaalgos/postproc.cc, spot/twaalgos/postproc.hh: Implement
the CoBuchi option.
* python/spot/__init__.py: Support it in Python.
* bin/common_post.cc: Add support for --buchi.
* bin/autfilt.cc: Remove the --dca option.
* tests/core/dca.test, tests/python/automata.ipynb: Adjust and add
more tests.  In particular, add more complex persistence and
recurrence formulas to the list of dca.test.
* tests/python/dca.test: Adjust and rename to...
* tests/core/dca2.test: ... this.  Add more tests, to the point
that this is now failing, as described in issue #317.
* tests/python/dca.py: Remove.
* tests/Makefile.am: Adjust.

tests/core/dca2.test

@@ -0,0 +1,75 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2017, 2018 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/>.
+
+. ./defs
+set -e
+
+cat >l_formulas <<'EOF'
+FG!b
+FGc
+F(a | Gb)
+XF(b & Ga)
+a | c | FG(!b & !c)
+!a | FGb
+F((!a & ((c & F!b) | (!c & Gb))) | (a & ((c & Gb) | (!c & F!b))))
+F((c & F!b) | (!c & Gb))
+F((!c R a) W G!b)
+FG(((!b | (c M b)) & X(c & Xa)) | (b & (!c W !b) & X(!c | X!a)))
+(Ga M c) M ((!b & Fb) M F(a | !b))
+(Gb | X(!b M X!b)) M ((b & c) | (!b & !c))
+F(c R (X!c W Fb))
+XF!c & F(Fb R a)
+(!c M F(b & Ga)) W (b U a)
+EOF
+
+cat >r_formulas <<'EOF'
+GF(b | GF!c)
+!b & G(G!c | XFc)
+GF(b | c | (!c & XFb))
+GFc | G(!b | !c)
+G(Gb | Fc)
+G(c | (c R Xc) | XF(b & !c))
+Gc R XFb
+G(c | (!b M (GFc | G!c)))
+F(((c W Xb) & F(b R !c)) | ((!c M X!b) & G(!b U c)))
+EOF
+
+while read l_f; do
+    ltl2tgba --parity='max odd' "$l_f" > l.hoa
+    autfilt -q --acceptance-is='Fin(0) | Inf(1)' l.hoa
+    while read r_f; do
+        # Dualizing a deterministic transition-based parity automaton
+        # to obtain a transition-based deterministic streett
+        # automaton.  What we want to avoid as much as possible is
+        # weak automata, because l.hoa is already weak and that would
+        # make the sum/product weak as well.
+        ltl2tgba "$r_f" -D --parity='min odd' | autfilt --dualize --gsa > r.hoa
+        # Streett & Streett
+        autfilt r.hoa --name="($l_f)&!($r_f)" --product=l.hoa -S > and.hoa
+        autfilt -q --acceptance-is=Streett and.hoa
+        # Streett | Streett
+        autfilt r.hoa --name="($l_f)|!($r_f)" --product-or=l.hoa -S > or.hoa
+        autfilt -q -v --acceptance-is=Streett or.hoa
+
+        autcross --language-preserved --verbose -F or.hoa -F and.hoa \
+                 'autfilt %H --stats=%M | ltl2tgba >%O' \
+                 'autfilt --cobuchi' 'autfilt --cobuchi -D'
+    done <r_formulas
+done <l_formulas