WRAP

	tells the turtle to enter wrap mode:  From now on, if the turtle
	is asked to move past the boundary of the graphics window, it
	will "wrap around" and reappear at the opposite edge of the
	window.  The top edge wraps to the bottom edge, while the left
	edge wraps to the right edge.  (So the window is topologically
	equivalent to a torus.)  This is the turtle's initial mode.
	Compare WINDOW and FENCE.

