* Merge from Debian unstable. The remaining Ubuntu changes are:
  - debian/{libsane,sane-utils}.README.Debian: Remove hotplug
    references,
  - debian/{libsane.dirs.linux,rules}: Ship udev rules only,
  - debian/libsane.postinst: Clean up old hotplug directories
    (not bailing where they're non-empty),
  - debian/patches/30_udev_long_comment_lines.dpatch: Prefer
    to debian/patches/25_udev_rules_line_length.dpatch,
  (Closes Ubuntu: #56317, #59141, #59390, #59753).