which produces a token [SEMI]. The parser SEMI to appear in three places:
after a declaration; after a rule; after a producer. Only two grammars in
the test suite have required changes.

It is replaced with [Positions.import] in a singleton list.

[InputFile.get_file_contents] is no longer published.

MenhirLib remains under LGPL with a linking exception.
MenhirSdk is considered part of the Generator.
Updated the header of every source file under version control.

Use a new type [input_file] instead, which records the file's name and index
on the command line.
This allows fixing a bug in [UnparameterizedPrinter] where [List.sort] was
used with a non-transitive "ordering".

They need not be exposed outside.

Also, fix the test that $i is within range -- it was incomplete.

  (Now uses the Str module.)

- Lexer.check_producers_indices: New. Are $i keywords correctly used?

- yacc-parser/fancy-parser: Turn the type of actions' semantic values
  into arrows to delay the checking of $i keywords from lexing to
  parsing.