Add missing call to cairo_surface_reference

This comes from the mailing-list (Thanks to Fred Bca):

Hi,

I am not sure if it is still the process to post patches on the mailing list, but I hope so. The recent merge request #52 (closed) (!52 (merged)) causes crashes because of a missing call to cairo_surface_reference in cairo_quartz_image_surface_create (since the original surface is destroyed by the quartz_image_surface, it should be referenced first). Please find a patch below to fix the problem:

--- cairo-quartz-image-surface.c +++ cairo-quartz-image-surface.c @@ -373,0 +374,2 @@ cairo_quartz_image_surface_create (cairo_surface_t

• // reference image surface - will be released in surface_destroy
• cairo_surface_reference (surface); -- cairo mailing list