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/defs.in

@@ -1,100 +0,0 @@
-# -*- mode: shell-script; coding: utf-8 -*-
-# Copyright (C) 2009, 2010, 2012, 2013, 2015 Laboratoire de Recherche
-# et Développement de l'Epita (LRDE).
-# Copyright (C) 2003, 2004, 2006 Laboratoire d'Informatique de Paris 6 (LIP6),
-# département Systèmes Répartis Coopératifs (SRC), Université Pierre
-# et Marie Curie.
-#
-# 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/>.
-
-# Ensure we are running from the right directory.
-test -f ./defs || {
-   echo "defs: not found in current directory" 1>&2
-   exit 1
-}
-
-# If srcdir is not set, then we are not running from `make check'.
-if test -z "$srcdir"; then
-   # compute $srcdir.
-   srcdir=`echo "$0" | sed -e 's,/[^\\/]*$,,'`
-   test $srcdir = $0 && srcdir=.
-fi
-
-# Ensure $srcdir is set correctly.
-test -f $srcdir/defs.in || {
-   echo "$srcdir/defs.in not found, check \$srcdir" 1>&2
-   exit 1
-}
-
-echo "== Running test $0"
-
-me=`echo "$0" | sed -e 's,.*[\\/],,;s/\.test$//'`
-
-testSubDir=$me.dir
-chmod -R a+rwx $testSubDir > /dev/null 2>&1
-rm -rf $testSubDir > /dev/null 2>&1
-mkdir $testSubDir
-cd $testSubDir
-
-# Adjust srcdir now that we are in a subdirectory.  We still want
-# $srcdir to point to the source directory corresponding to the build
-# directory that contains $testSubDir.
-case $srcdir in
-  [\\/$]* | ?:[\\/]* );;
-  *) srcdir=../$srcdir
-esac
-
-DOT='@DOT@'
-top_builddir='../@top_builddir@'
-LBTT="@LBTT@"
-LBTT_TRANSLATE="@LBTT_TRANSLATE@"
-VALGRIND='@VALGRIND@'
-SPIN='@SPIN@'
-LTL2BA='@LTL2BA@'
-PYTHON='@PYTHON@'
-top_srcdir='../@top_srcdir@'
-
-# The test cases assume these variable are undefined
-unset SPOT_DOTEXTRA
-unset SPOT_DOTDEFAULT
-
-need_lbtt()
-{
-  # LBTT may not have been installed or compiled.
-  ("$LBTT" --version) || exit 77
-}
-
-run()
-{
-  expected_exitcode=$1
-  shift
-  exitcode=0
-  if test -n "$VALGRIND"; then
-    exec 6>valgrind.err
-    GLIBCPP_FORCE_NEW=1 \
-    ../../libtool --mode=execute \
-    $VALGRIND --tool=memcheck --leak-check=yes --log-fd=6 -q "$@" ||
-      exitcode=$?
-    cat valgrind.err 1>&2
-    test -z "`sed 1q valgrind.err`" || exit 50
-    rm -f valgrind.err
-  else
-    "$@" || exitcode=$?
-  fi
-  test $exitcode = $expected_exitcode || exit 1
-}
-
-set -x