This allows to write `Stdlib.List.map :: {Int Bool}`. The previous syntax,
`Stdlib.List.map with { Int Bool }` is ambiguous with the `match ... with` and needs
arbitrary look-ahead. It can still be written, with explicit parentheses.

Add a new flag --binarystub to allow creating the stubs in binary format instead of OCaml text source.

let x & t = is now allowed.

default to Latin1 for compatibility.