code: function(ctor, superCtor)
  	{
  		var f = function() {};
  		f.prototype = superCtor.prototype;
  		
  		ctor.prototype = new f();
  		ctor.prototype.constructor = ctor;
  	}
docs: Function: extend
  
  Assigns a copy of the superclass prototype to the subclass prototype.
  Note that this does not call the constructor of the superclass at this
  point, the superclass constructor should be called explicitely in the
  subclass constructor. Below is an example.
  
  (code)
  MyGraph = function(container, model, renderHint, stylesheet)
  {
  mxGraph.call(this, container, model, renderHint, stylesheet);
  }
  
  mxUtils.extend(MyGraph, mxGraph);
  (end)
  
  Parameters:
  
  ctor - Constructor of the subclass.
  superCtor - Constructor of the superclass.