[ansel] Patch for user pref image type

[Chuck Hagenbuch]

Quoting "Heath S. Hendrickson" <heath at outerspaceconsultants.com>:

> The attached patch goes with the user pref patches submitted earlier.
> This makes it user configurable what format should be used for the
> system created image files (_thumb and _screen).

I still don't like this, as there's no guarantee that the chosen format is
actually available, thus making it entirely possible for a user to break their
gallery without any real indication thereof.

-chuck

--
Charles Hagenbuch, <chuck at horde.org>
"Here, I brought some cole slaw. It's made from peeeooople! Just kidding."