[cairo] Use _cairo_rectangle_intersect in more places for intersection checking

[Jeff Muizelaar]

On Mon, Oct 22, 2007 at 10:52:46PM +0000, BJörn Lindqvist wrote:
> Hello,
> 
> Here is two patches, the first modifies _cairo_rectangle_intersect()
> so that TRUE or FALSE is returned whether the rectangles intersect or
> not. Just like about five million other rectangle intersection
> functions work.
> 
> Which is important for the second patch that modifies all
> _cairo_*_get_image() functions so that they now use the
> _cairo_rectangle_intersect() function for doing intersection checking
> instead of spelling it out themselves.
> 
> The benefit is that quite a few lines of code are removed. I also
> added some docstrings to some touched functions because I found it
> hard to tell what those functions were doing.

Nit: Both patches add some inconsistent indentation.

-Jeff