[cairo] Extend methods for gradient patterns

[Torsten Schoenfeld]

On 31.03.2010 23:05, Bill Spitzak wrote:
> Clicking on "cairo_pattern_set_extend()"
> http://cairographics.org/manual/cairo-pattern.html#cairo-pattern-set-extend
> reveals text that says "The default extend mode is CAIRO_EXTEND_NONE for
> surface patterns and CAIRO_EXTEND_PAD for gradient patterns." So I would
> say the first page is wrong and those should be moved up under pattern
> or replicated under cairo_gradient_t

Actually, from reading the code and running tests, it seems it is legal 
to call [sg]et_extend and [sg]et_filter on all pattern types.  Hence the 
attached patch.