d> fix image_change_from_image (to do this need a pixbuf_renderer_move_image).
d> fix broken zoom out drawing when using source tiles.
d> fix 2pass zoom when using source tiles and zoomed out (not always rendering second pass)
+ d> pixbuf_renderer_move should be clearing the tiles of the source image since they are no longer
+ valid and are then wasting memory (for example when full screen is active).
> image.c:
d> need to keep a list of ImageWindows and provide function to sync options to each object.