remove a GCC 4.6 workaround

* src/twa/twagraph.hh (namer): Use a template alias instead
of a trait.
* src/twa/twagraph.cc, src/parseaut/parseaut.yy,
src/twaalgos/ltl2tgba_fm.cc: Adjust.

src/parseaut/parseaut.yy

@@ -49,7 +49,7 @@
     typedef std::map<std::string, bdd> formula_cache;
 
     typedef std::pair<int, std::string*> pair;
-    typedef typename spot::twa_graph::namer<std::string>::type named_tgba_t;
+    typedef spot::twa_graph::namer<std::string> named_tgba_t;
 
     // Note: because this parser is meant to be used on a stream of
     // automata, it tries hard to recover from errors, so that we get a

src/twa/twagraph.cc

@@ -24,8 +24,8 @@
 namespace spot
 {
   void
-  twa_graph::release_formula_namer(typename namer<const ltl::formula*>::type*
-				   namer, bool keep_names)
+  twa_graph::release_formula_namer(namer<const ltl::formula*>* namer,
+				   bool keep_names)
   {
     if (keep_names)
       {

src/twa/twagraph.hh

@@ -204,34 +204,30 @@ namespace spot
       last_support_conditions_input_ = 0;
     }
 
-    // FIXME: Once we ditch GCC 4.6, we can using a template aliases
-    // (supported from GCC 4.7 onward) instead of this.
+#ifndef SWIG
     template <typename State_Name,
 	      typename Name_Hash = std::hash<State_Name>,
 	      typename Name_Equal = std::equal_to<State_Name>>
-    struct namer
-    {
-      typedef named_graph<graph_t, State_Name, Name_Hash, Name_Equal> type;
-    };
+    using namer = named_graph<graph_t, State_Name, Name_Hash, Name_Equal>;
 
     template <typename State_Name,
 	      typename Name_Hash = std::hash<State_Name>,
 	      typename Name_Equal = std::equal_to<State_Name>>
-    typename namer<State_Name, Name_Hash, Name_Equal>::type*
+    namer<State_Name, Name_Hash, Name_Equal>*
     create_namer()
     {
       return new named_graph<graph_t, State_Name, Name_Hash, Name_Equal>(g_);
     }
 
-    typename namer<const ltl::formula*>::type*
+    namer<const ltl::formula*>*
     create_formula_namer()
     {
       return create_namer<const ltl::formula*>();
     }
 
     void
-    release_formula_namer(typename namer<const ltl::formula*>::type* namer,
-			  bool keep_names);
+    release_formula_namer(namer<const ltl::formula*>* namer, bool keep_names);
+#endif
 
     graph_t& get_graph()
     {

src/twaalgos/ltl2tgba_fm.cc

@@ -110,7 +110,7 @@ namespace spot
 
     class ratexp_to_dfa
     {
-      typedef typename twa_graph::namer<const formula*>::type namer;
+      typedef twa_graph::namer<const formula*> namer;
     public:
       ratexp_to_dfa(translate_dict& dict);
       std::tuple<const_twa_graph_ptr, const namer*, const state*>