* new-variables-issue-26:
  Rework the type variable infrastructure. Remove it from the type structure and have the auxiliary function cache the results as needed.
  Properly check constraints on monomprhic variable during constraint generation: when a constraint 'a < t or t < 'a with 'a being monomorphic occurs during constraint generation, we check whether it holds for all 'a, that is we use plain subtyping. (It generalizes the fact that 'a < Any or Empty < 'a hold for monomorphic variables, but also accounts for constraints such as 'a < 'a | t and so on).

Conflicts:
	types/types.ml