Special treatment of tuples in the type 'typ' (type.ml) eliminated

Tuple types are normal types now generated from the class TUPLE

    A: ANY; B:ANY
    immutable class TUPLE[A,B] end

A tuple has always two generic parameters. The nesting of tuples is right
associative, i.e. we write

    (A,B,C)

instead of

    (A,(B,C))

The same applies to function types, i.e. (A,B,C)->D is a shorthand for
(A,(B,C))->D.

	modified:   ocaml/class_table.ml
	modified:   ocaml/class_table.mli
	modified:   ocaml/feature_table.ml
	modified:   ocaml/type.ml