Add options --pre-depend and --infer-output MLIFILE
- Add option --pre-depend to stop after generating an ML grammar file and an MLI interface to be used by ocamldep
- Add option --infer-output MLIFILE to be used in combination with --infer to use as output instead of calling ocamlc. This MLIFILE can be generated by compiling the ML file (without the MLI) generated by --pre-depend.
These options can be combined to completely avoid calling ocamlc and ocamldep within menhir.