add initial version of gdkpixbuf loader for gtk that is capable of loading AVI and...

add initial version of gdkpixbuf loader for gtk that is capable of loading AVI and mpeg videos as GdkPixbufAnimation....

Original commit message from CVS:
add initial version of gdkpixbuf loader for gtk that is capable of loading AVI and mpeg videos as GdkPixbufAnimation. I'm not sure if such a thing would be useful or too much trouble, so I'll throw it at enough testers to figure it out ;) We might want to disable it by defualt though in the future. (Currently there is not even a configure switch implemented to disable it.)
This includes a fix to not use GError in gstgdkpixbuf's typefind function and to only return GST_TYPE_FIND_MINIMUM when doing typefinding via gdk as this breaks quite a bit with the GStreamer loader installed.