twa: fix duplicate propositions in ap()

Calling register_ap() with same atomic proposition several time, for
instance via copy_ap() in a product, would create duplicate atomic
propositions.  This fix will be exercised by the next patch.

* spot/twa/twa.hh: Here.
* spot/twaalgos/compsusp.cc, spot/twaalgos/ltl2taa.cc: Fix
to correctly register atomic propositions.
* NEWS: Mention it.

NEWS

@@ -71,6 +71,9 @@ New in spot 1.99.6a (not yet released)
 
   Bug fixes:
 
+  * twa::ap() would contain duplicates when an atomic proposition
+    was registered several times.
+
 New in spot 1.99.6 (2015-12-04)
 
   Command-line tools:

spot/twa/twa.hh

@@ -597,9 +597,13 @@ namespace spot
     /// \return The BDD variable number.
     int register_ap(formula ap)
     {
-      aps_.push_back(ap);
+      int res = dict_->has_registered_proposition(ap, this);
-      int res = dict_->register_proposition(ap, this);
+      if (res < 0)
-      bddaps_ &= bdd_ithvar(res);
+	{
+	  aps_.push_back(ap);
+	  res = dict_->register_proposition(ap, this);
+	  bddaps_ &= bdd_ithvar(res);
+	}
       return res;
     }
 
@@ -720,7 +724,6 @@ namespace spot
 
     void copy_ap_of(const const_twa_ptr& a)
     {
-      get_dict()->register_all_propositions_of(a, this);
       for (auto f: a->ap())
 	this->register_ap(f);
     }

spot/twaalgos/compsusp.cc

@@ -164,9 +164,19 @@ namespace spot
 					false));
 
       twa_graph_ptr res = make_twa_graph(dict);
-      dict->register_all_variables_of(left, res);
+      {
-      dict->register_all_variables_of(right, res);
+	// Copy all atomic propositions, except the one corresponding
-      dict->unregister_variable(bdd_var(v), res);
+	// to the variable v used for synchronization.
+	int vn = bdd_var(v);
+	assert(dict->bdd_map[vn].type = bdd_dict::var);
+	formula vf = dict->bdd_map[vn].f;
+	for (auto a: left->ap())
+	  if (a != vf)
+	    res->register_ap(a);
+	for (auto a: right->ap())
+	  if (a != vf)
+	    res->register_ap(a);
+      }
 
       unsigned lsets = left->num_sets();
       res->set_generalized_buchi(lsets + right->num_sets());

spot/twaalgos/ltl2taa.cc

@@ -72,6 +72,7 @@ namespace spot
 	    SPOT_UNIMPLEMENTED();
 	  case op::ap:
 	    {
+	      res_->register_ap(f);
 	      if (negated_)
 		f = formula::Not(f);
 	      init_ = f;