graphics/darktable: Update to 4.2.0
Release notes:
https://github.com/darktable-org/darktable/releases/tag/release-4.2.0
The work was done by Matthias Andree (mandree@) in
graphics/darktable42. Some of the style fixes were added in a separate
commit. Thank you Matthias!
The temporary port graphics/darktable42 can be removed at the same
time, now that the main port is up-to-date.
Submitted by: mandree@