code: public static Parser<Void> blockComment(Parser<Void> begin, Parser<Void> end, Parser<?> commented) {
      return Parsers.sequence(begin, end.not().next(commented).skipMany(), end);
    }
docs: A scanner for a non-nestable block comment that starts with {@code begin} and ends with
  {@code end}.
  
  @param begin begins a block comment
  @param end ends a block comment
  @param commented the commented pattern.
  @return the Scanner for the block comment.