Update to OCaml 4.07 #6
Description
Update to OCaml 4.07 (or at least 4.03) to get access to the improvements to stdlib and some packages (e.g. dune).
Raspbian only has OCaml 4.02 and opam in its repositories which should be enough to compile OCaml 4.07 or load it via opam but this did not work previously for some reason.