Implement advanced OCaml utop REPL (autocompletion, etc).
OCaml utop: implement highlighting of errors, fix handling of multiline input.
OCaml: better highlighting.
Merge pull request #283 from whitequark/master

Implement advanced OCaml utop REPL (autocompletion, etc)
st2 compat
add default extend_env values to OCaml utop repl

it should work OOTB with standard opam installation