* operations/external/ff-load.c: (get_cached_region),
* operations/external/jpg-load.c: (get_cached_region),
* operations/external/png-load.c: (get_cached_region),
* operations/external/v4l.c: (get_cached_region): make these ops
request a cache the size of the bounding box of the file (only load
data once).

svn path=/trunk/; revision=2837