Use menhir-based parser instead of camlp4o

[seliopou]

The library uses camlp4o to parse locale definitions, which is a hinderance to both adoption (see tategakibunko/jingoo#19) as well as future maintenance. The parser should be ported to menhir or some such other parser library to break the dependency with camlp4o.

[rgrinberg]

+1, we should absolutely get rid of camlp4 where possible.

@michipili definitely a milestone before 1.0 IMO

[seliopou]

The grammar that the parser implements is documented here.

It took forever to find it. Enterprise software is terrifying.

[foretspaisibles]

@rgrinberg Agreed! #12.

[rgrinberg]

I have a branch (on top of #22) that replaces the camlp4 lexer with with the same lexer but without the syntax extension. It would still be nice to have a proper menhir based parser, but i think that should be enough to solve this problem for the medium term.

[rgrinberg]

We aren't using camlp4 anymore.