Dear maintainers, According to https://salsa.debian.org/science-team/vlfeat/-/blob/master/debian/README.source, sift was removed from the source due to patent issues. And now, according to https://www.cs.ubc.ca/~lowe/keypoints/, it expired as of March 7, 2020. Any plan to re-enable sift in vlfeat? Sincerely, Butui Hu