gray black image fails on old autocrop sw

The microfilm software uses a very early, preliminary version of Raj's
autocrop software.

For some unknown class of images there's a failure.

For example, see item
   http://www.archive.org/details/4625158
and in particular the log of pre-processing it:
   http://www.us.archive.org/log_show.php?task_id=30080277

It fails on image 46, which is basically black but with a little white or
gray on the left edge.

So: we could patch up the old version a little, or we could try to
migrate to the latest version.