Introduce osg::Object::asNode(), asNodeVisitor(), asStateAttribute() and asUniform() to replace dynamic_cast<> usage in Callback.cpp.

git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14902 16af8721-9629-0410-8352-f15c8da7e697

include/osg/Uniform

@@ -551,7 +551,15 @@ class OSG_EXPORT Uniform : public Object
 
         META_Object(osg, Uniform);
 
+        /** Convert 'this' into a Uniform pointer if Object is a Uniform, otherwise return 0.
+          * Equivalent to dynamic_cast<Uniform*>(this).*/
+        virtual Uniform* asUniform() { return this; }
 
+        /** convert 'const this' into a const Uniform pointer if Object is a Uniform, otherwise return 0.
+          * Equivalent to dynamic_cast<const Uniform*>(this).*/
+        virtual const Uniform* asUniform() const { return this; }
+
+        
         /** Set the type of glUniform, ensuring it is only set once.*/
         bool setType( Type t );