This function was basically never working correctly. Everything was
fixed by simulating the evas_object_image_render() workflow, but
instead of actually draw we just check the pixel transparency.
Bugs fixed:
* fails when image is scaled up (could segv) or down (incorrect values);
* fails when image is moved to negative x,y;
* fails when border was being used.
Now everything is fixed and seems to work properly, except I'm not
handling the map and get_pixels() cases, these are marked with ERR()
so we can fix them if someone needs.
SVN revision: 81410
Gustavo Sverzut Barbieri