Canvas: use new naGCSave/naGCRelease functions.

simgear/canvas/CanvasEventListener.cxx

@@ -43,14 +43,13 @@ namespace canvas
         "canvas::NasalEventListener: invalid function argument"
       );
 
-    _gc_key = sys_adapter->gcSave(_code);
+    _gc_key = naGCSave(_code);
   }
 
   //----------------------------------------------------------------------------
   NasalEventListener::~NasalEventListener()
   {
-    if( !_sys.expired() )
+    naGCRelease(_gc_key);
-      _sys.lock()->gcRelease(_gc_key);
   }
 
   //----------------------------------------------------------------------------

simgear/canvas/CanvasSystemAdapter.hxx

@@ -39,18 +39,6 @@ namespace canvas
 
       virtual naContext getNasalContext() const = 0;
 
-      /**
-       * Save passed reference to Nasal object from being deleted by the
-       * garbage collector.
-       */
-      virtual int gcSave(naRef r) = 0;
-
-      /**
-       * Release an object previously passed to ::gcSave to allow it being
-       * cleaned up by the garbage collector.
-       */
-      virtual void gcRelease(int key) = 0;
-
       /**
        * Call a Nasal function with the given environment and arguments.
        */