- from Module.xxx_to_string to Module.Print.string_of_xxxx
- from Module.print_xxx to Module.Print.pp_xx

- refactoring in types.ml
- add Types.squareapply
- other fixes

- refactoring in types.ml
- add Types.squareapply
- other fixes

Switch typesTest from OUnit to OUnit2 (mostly to get a correct exit value)

- Add delta as optional parameter to Tallying.talling.
- Add (++) product of two lazy types substitutions.
- Add (@@) application of a lazy type substition to a type.
- Add ($$) application of a explicit type substution to a type.

[TESTS][LAMBDA] add tests for comp of sigmas

[TESTS][LAMBDA] Add a test on comp of sigmas

	function so it's not working for now)
[TESTS][LAMBDA] Add chars (shows it should be easy to use the '<uident> syntax
	for type variables in CDuce)

Now we correctly distibguish polymorphic and monomorphic types and
set sigma substitutions accordingly

micro performance improvement