[isabelle-dev] NEWS: support for OCaml / OPAM

[Lars Hupel]

>   * How to re-init the opam installation, e.g. after changing
> ISABELLE_OCAML_VERSION (maybe even in ISABELLE_HOME_USER/etc/settings)?
>     (Presently I have just removed purged ISABELLE_OPAM_ROOT.)

I don't think purging the directory is necessary. It should work out of
the box. According to my experiments, opam will just install another
OCaml version side-by-side.

>   * Is the update of ~/.ocamlinit that is proposed by opam init required?

Probably not.