Merge the core and python tests in the tests/ directory

* tests/: Rename as...
* tests/core/: ... this.
* python/tests/: Rename as...
* tests/python/: ... this.
* python/tests/run.in: Move as...
* tests/run.in: This, and adjust.
* tests/Makefile.am: Adjust to run both core and python tests.
* configure.ac, README, debian/python3-spot.examples, debian/rules,
doc/org/tut.org, python/Makefile.am, spot/ltsmin/Makefile.am,
spot/ltsmin/kripke.test, spot/sanity/ipynb.test: Adjust.

tests/core/ltlcrossgrind.test

@@ -0,0 +1,36 @@
+#! /bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2014 Laboratoire de Recherche et Dévelopement to
+# 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 || exit 1
+
+set -e
+
+cat >fake <<EOF
+#!/bin/sh
+ltl2tgba -s -f "\$1" | sed 's/p0/p1/g'
+EOF
+
+chmod +x fake
+
+run 1 ltlcross -f 'p0 U p1' "./fake %f >%N" \
+"ltl2tgba -s -f %f >%N" --grind=bogus.grind
+
+echo p0 >exp
+diff bogus.grind exp