* Remove support for installing via ocamlfind.
* Remove PREFIX.
* Move the source of MenhirLib into lib/.
* Move the source of MenhirSdk into sdk/.
* Build and install everything using dune.
* Run all tests using dune. Reorganize the test directory.
* Move the old ocamlbuild demos to a subdirectory.
* Introduce [make versions] to test Menhir with multiple versions of OCaml.
* Update the release scripts.