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/ltl2tgba.py

@@ -1,8 +1,8 @@
-# -*- mode: python; coding: iso-8859-1 -*-
-# Copyright (C) 2009, 2010 Laboratoire de Recherche et Développement
-# de l'Epita (LRDE).
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2009, 2010, 2012 Laboratoire de Recherche et
+# Développement de l'Epita (LRDE).
 # Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris 6 (LIP6),
-# département Systèmes Répartis Coopératifs (SRC), Université Pierre
+# département Systèmes Répartis Coopératifs (SRC), Université Pierre
 # et Marie Curie.
 #
 # This file is part of Spot, a model checking library.
@@ -30,7 +30,7 @@ import getopt
 import spot
 
 def usage(prog):
-    print "Usage: ", prog, """ [OPTIONS...] formula
+    sys.stderr.write("""Usage: %s [OPTIONS...] formula
 
 Options:
   -a   display the acceptance_conditions BDD, not the reachability graph
@@ -41,7 +41,8 @@ Options:
   -r   display the relation BDD, not the reachability graph
   -R   same as -r, but as a set
   -t   display reachable states in LBTT's format
-  -v   display the BDD variables used by the automaton"""
+  -v   display the BDD variables used by the automaton
+""" % prog)
     sys.exit(2)
 
 
@@ -122,12 +123,12 @@ if f:
         if concrete:
             spot.bdd_print_set(cout, concrete.get_dict(),
                                concrete.get_core_data().relation)
-        print
+        spot.nl_cout()
     elif output == 4:
         if concrete:
             spot.bdd_print_set(cout, concrete.get_dict(),
                                concrete.get_core_data().acceptance_conditions)
-        print
+        spot.nl_cout()
     elif output == 5:
         a.get_dict().dump(cout)
     elif output == 6: