- 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] Improved pp_lambda; update a test

	execution yet

micro performance improvement

Conflicts:
	types/types.ml
	types/types.mli

and Cap (to fix)

  to detect that we have the most precise solution
* Apply clean_type more agressively but on smaller types, for each of the partial solutions
  rather than on the (big) intersection of all the solutions.
* Small optimisation in substitutefree: do not do anything if the type has no variables