MRI: {Rect,Color,Tone}#initialize_copy instead of #clone

- removed unused CLONE_FUNC
- #initialize_copy should be used instead of #clone. It's the general way to do it and the RGSS defines it, too

Or was there a reason for directly defining #cloneinstead?

(Your code is weird. :3 Well, the RGSS is too but not in that way. And I don't mean the coding style! Rather stuff like ```setPrivateData```. Why are two objects used? One object and one ivar called PRIV_IV which holds the data pointer, even though you could just use one object for that.)