fixed Sprite.set(Sprite) so that it now also copies regionWidth and regionHeight

If the method's documentation declares that it will:

```java
	/** Make this sprite a copy in every way of the specified sprite */
```
…then the critical fields regionWidth and regionHeight should also be
copied from the incoming sprite. Their absence makes Sprite's copy
constructor (which uses set) produce buggy, zero-width, zero-height
textures that are invisible when rendered.