md_parser.ml: It seems I've just managed to correctly implement the right semantics for lists...

# Md_parser.parse (Md_lexer.lex_from_string "* Bonjour\n* Hello\n* plop\n * xx x\n     * PLOP \n   * HEY  ");;
- : Md_parser.md =
[Md_parser.Ul
  [Md_parser.Li [Md_parser.Text "Bonjour"];
   Md_parser.Li [Md_parser.Text "Hello"];
   Md_parser.Li
    [Md_parser.Text "plop";
     Md_parser.Ul
      [Md_parser.Li
        [Md_parser.Text "xx"; Md_parser.Text " x";
         Md_parser.Ul [Md_parser.Li [Md_parser.Text "PLOP"]];
         Md_parser.Ul [Md_parser.Li [Md_parser.Text "HEY"]]]]]]]