Migrate off camlp4

[XVilka]

Camlp4 release for OCaml 4.08 is the last release ever - see the official announcement. It is recommended to port the code to use ppx (extension points), or any external parser (like mehrir, sedlex, ocamllex, ansgtrom, etc).

Latest available package is 3.4 and still depends on camlp4: http://opam.ocaml.org/packages/ocapic/

P.S. you might also want to switch to Dune build system to simplify building, maintenance, and even publishing (using dune-release tool).