message: add some trait derivings
diff: @@ -102,6 +102,7 @@ fn max_lookups_per_row<F>(kinds: &Vec<Vec<JointLookup<F>>>) -> usize {
  kinds.iter().fold(0, |acc, x| std::cmp::max(x.len(), acc))
  }
  +#[derive(Copy, Clone, Debug)]
  pub enum LookupsUsed {
  Single,
  Joint,
  