hoa: use the tgba_digraph interface to save automata

* src/tgbaalgos/hoa.cc: Here.
* src/tgbatest/det.test, src/tgbatest/hoaparse.test,
src/tgbatest/monitor.test, doc/org/oaut.org: Adjust.

src/tgbatest/monitor.test

@@ -1,7 +1,7 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2014 Laboratoire de Recherche et Développement de
-# l'Epita (LRDE).
+# Copyright (C) 2014, 2015 Laboratoire de Recherche et Développement
+# de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
 #
@@ -47,16 +47,16 @@ expect ../../bin/ltl2tgba --monitor a --hoa<<EOF
 HOA: v1
 name: "a"
 States: 2
-Start: 0
+Start: 1
 AP: 1 "a"
 acc-name: all
 Acceptance: 0 t
 properties: trans-labels explicit-labels state-acc deterministic
 --BODY--
 State: 0
-[0] 1
+[t] 0
 State: 1
-[t] 1
+[0] 0
 --END--
 EOF