* 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]).
LexToken, AST: Tiny refactoring.
Bug: Added the making of the AST node PBytes.
Parser: The rule "pattern" was not properly stratified (the
constructor "PCons" was always produced, even when no consing was
done (now a fall-through to "core_pattern").
Bug: When sharing the lexers between Ligodity and Pascaligo, a
regression was introduced with the lexing of symbols. Indeed,
symbols specific to Ligodity (like "<>") and
Pascaligo (like "=/=") were scanned, but the
function "LexToken.mk_sym" for each only accepted their own,
yielding to an assertion to be invalidated. Fix: I created an
error "sym_err" now to gracefully handle that situation and
provide a hint to the programmer (to wit, to check the LIGO
syntax in use).
WIP: Started to write pretty-printing functions for the nodes of
the AST.
CLI: The option "--verbose=ast" now calls that function instead
of printing the tokens from the AST. When the pretty-printer is
finished, the option for printing the tokens will likely
be "--verbose=ast-tokens".
