Author : Olivier Langlois <olanglois@sympatico.ca>

<06/10/98>
I have added a new function (apply()) that call a function for all
objects in the wireframe

<02/09/98>
I have added a counter in the WireFrame class that is
incremented each time the
add_*() methods are called and reseted when clear() is called.
I also added the method entries() that return the counter's value.