Make all python code compatible with Python 2.x and Python 3.x.

* wrap/python/buddy.i (__le__, __lt__, __eq__, __ne__, __ge__
__gt__): New operators for bdd.
* wrap/python/spot.i (__le__, __lt__, __eq__, __ne__, __ge__
__gt__, __hash__): New operators for formula.
(nl_cout, nl_cerr): New functions.
* wrap/python/tests/bddnqueen.py,
wrap/python/tests/interdep.py, wrap/python/tests/ltl2tgba.py,
wrap/python/tests/ltlparse.py, wrap/python/tests/ltlsimple.py,
wrap/python/tests/minato.py, wrap/python/tests/modgray.py: Adjust
to the new print syntax by using sys.output.write() or nl_cout()
instead.
* wrap/python/tests/optionmap.py: Remove all print calls.
* wrap/python/ajax/spot.in: Massive adjustments in order to work
with both Python 2 and 3.  In python 3, reopening stdout as
unbuffered requires it to be open as binary, which in turns
requires any string output to be encoded manually.  BaseHTTPServer
and CGIHTTPServer have been merged into http.server, so we have
to try two different import syntaxes.  execfile no longer exists,
so it has to be emulated.
This also fixes two bugs where the script would segfault on
empty input, or when calling Tau03 on automata with less then
one acceptance conditions.

wrap/python/tests/bddnqueen.py

@@ -1,6 +1,6 @@
 # -*- mode: python; coding: utf-8 -*-
-# Copyright (C) 2010, 2011 Laboratoire de Recherche et Développement
-# de l'EPITA.
+# Copyright (C) 2010, 2011, 2012 Laboratoire de Recherche et
+# Développement de l'EPITA.
 # Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris 6
 # (LIP6), département Systèmes Répartis Coopératifs (SRC), Université
 # Pierre et Marie Curie.
@@ -27,6 +27,7 @@
 
 import sys
 from buddy import *
+from spot import nl_cout
 
 # Build the requirements for all other fields than (i,j) assuming
 # that (i,j) has a queen.
@@ -89,15 +90,15 @@ for i in side:
 # Build requirements for each variable(field).
 for i in side:
     for j in side:
-        print "Adding position %d, %d" % (i, j)
+        sys.stdout.write("Adding position %d, %d\n" % (i, j))
         build(i, j)
 
 # Print the results.
-print "There are", bdd_satcount(queen), "solutions"
-print "one is:"
+sys.stdout.write("There are %d solutions, one is:\n" %
+                 bdd_satcount(queen))
 solution = bdd_satone(queen)
 bdd_printset(solution)
-print
+nl_cout()
 
 # Cleanup all BDD variables before calling bdd_done(), otherwise
 # bdd_delref will be called after bdd_done() and this is unsafe in