Introduce NodeVisitor::className and libraryName()

include/osg/NodeVisitor

@@ -42,6 +42,10 @@ class Transform;
 class Camera;
 class CameraView;
 
+#define META_NodeVisitor(library,name) \
+        virtual const char* libraryName() const { return #library; }\
+        virtual const char* className() const { return #name; }
+
 /** Visitor for type safe operations on osg::Nodes.
     Based on GOF's Visitor pattern. The NodeVisitor 
     is useful for developing type safe operations to nodes
@@ -82,6 +86,12 @@ class OSG_EXPORT NodeVisitor : public virtual Referenced
         NodeVisitor(VisitorType type,TraversalMode tm=TRAVERSE_NONE);
         
         virtual ~NodeVisitor();
+        
+        /** return the library name/namespapce of the visitor's. Should be defined by derived classes.*/
+        virtual const char* libraryName() const { return "osg"; }
+
+        /** return the name of the visitor's class type. Should be defined by derived classes.*/
+        virtual const char* className() const { return "NodeVisitor"; }
 
         /** Method to call to reset visitor. Useful if your visitor accumulates
             state during a traversal, and you plan to reuse the visitor.