* I added CLI option "--mono" to select the monolithic API of Menhir.
* I added a field "win" to the state of the lexer (a two-token
window for error reporting).
* I escaped LIGO strings before making them OCaml strings (for
example for printing).
I also had to remove the keywords [Down], [Fail] and [Step] in
PascaLIGO that made a mysterious and unwanted come back. (I did not
bother with [git blame]).
