examples/multi_os relies on unmaintained ufraw-batch

[wpferguson]

examples/multi_os uses ufraw-batch to extract the embedded jpeg from the camera raw. ufraw hasn't been maintained since 2016. The code was forked and is now maintained as nufraw. This, as well as ufraw, rely on a gtk widget, gtkimageview, that is a gnome project(?).

dcraw is still maintained and in most (all) distributions repositories. It is capable of extracting the embedded image, making it a viable replacement for ufraw-batch.

[wpferguson]

Superseded by #398