v19

• Compatibility with OCaml 5.0

• Add String.{hash, seeded_hash}

• Restore compatibility with OCaml 3.07, and fix order execution for
  Set and Map.{iter, fold, filter_map} on OCaml 3.07

• Updated port to dune
  (Marek Kubica, #16,
  #19
  with contribution from Kate,
  #21)

• Add support for flambda2
  (Guillaume Bury, #14)

• Prevent replacing /dev/null/ by a regular file when ./configure is
  run as root
  (reported by Marc Chevalier, ocaml/ocaml#11302)