Adding function to canonicalize an automaton.

* src/tgbaalgos/are_isomorphic.cc, src/tgbaalgos/are_isomorphic.hh,
src/bin/autfilt.cc: are_isomorphic now uses canonicalize. It returns a
bool, because the mapping cannot be deduced easily from the
canonicalized automaton.
* src/graph/graph.hh: Add equality operator to trans_storage_t
for easy comparison of transition vectors.
* src/tgba/tgbagraph.hh: Add equality operator to tgba_graph_trans_data
and to tgba_digraph.
* src/tgbaalgos/canonicalize.cc, src/tgbaalgos/canonicalize.hh:
New files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbatest/isomorph.test: Test them.

src/tgbaalgos/are_isomorphic.hh

@@ -26,16 +26,18 @@
 namespace spot
 {
   /// \ingroup tgba_misc
-  /// \brief Check whether two automate are isormorphic.
+  /// \brief Check whether two automata are isomorphic.
   ///
-  /// Return an isomorphism between a1 and a2 if such an isomorphism
-  /// exists.  Otherwise, return an empty vector.
-  ///
-  /// \return a vector indexed by states of \a a1, and containing
-  /// states of \a a2.
-  SPOT_API std::vector<unsigned>
-  are_isomorphic(const const_tgba_digraph_ptr a1,
-		 const const_tgba_digraph_ptr a2);
+  /// Two automata are considered isomorphic if there exists a bijection f
+  /// between the states of a1 and the states of a2 such that for any pair of
+  /// states (s1, s2) of a1, there is a transition from s1 to s2 with
+  /// condition c and acceptance set A iff there is a transition with
+  /// condition c and acceptance set A between f(s1) and f(s2) in a2.
+  /// This can be done simply by checking if
+  /// canonicalize(aut1) == canonicalize(aut2).
+  SPOT_API bool
+  are_isomorphic(const const_tgba_digraph_ptr aut1,
+		 const const_tgba_digraph_ptr aut2);
 }
 
 #endif