distinct arguments to constructZTree, so that the damageRect can
	really reflect your clip rect.
	This allows me to prune out layers that are clipped so
	that if x,y aren't inside the clip rect, the layer doesn't get added to
	the list.

	This patch also makes the "clip" property apply to the element that specifies the clip instead of to the element's kids.  This is ambiguous in the spec, but it turns out other browsers do it this way, so there really is an interpretation that must be followed. :)

	Reviewed by darin

        * khtml/rendering/render_layer.cpp:
        (RenderLayer::nodeAtPoint):
        (RenderLayer::constructZTree):
        * khtml/rendering/render_layer.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@3236 268f45cc-cd09-0410-ab3c-d52691b4dbfc