RAWTranslator: switch to libraw as backend when available

tested with .cr2 and .dng single pictures.

Change-Id: I9a4802300fd2afe14c085ca18faa8a1e20c52bfd
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4452
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>