Migrate from ulex to sedlex

[XVilka]

Long story short - ulex is dying, mainstream depends on the camlp4, which is dead, fork depends on the camlp5, which seems dead too. This prevents from porting to more modern OCaml versions and dependencies versions.

See these links for more information:

• https://discuss.ocaml.org/t/camlp5-and-ocaml-4-08/3985/4
• Rename ulex-camlp5 into ulex ocaml/opam-repository#14351

Sedlex is an active maintained project by OCaml community: https://github.com/ocaml-community/sedlex

[msprotz]

Hello,

Yes, eventually I'd like to move. Is there any chance you could submit a pull request?

Thanks,

Jonathan

[s-zanella]

Updated PR in #144

[XVilka]

Perfect! Thank you.