combination of a trace with functions for handling unknown code and converting to and from summaries

`type action````=`

`|` `Propagate_to_actual of int` | (** Propagate taint from all actuals to the actual with the given index *)
`|` `Propagate_to_receiver` | (** Propagate taint from all non-receiver actuals to the receiver actual *)
`|` `Propagate_to_return` | (** Propagate taint from all actuals to the return value *)

``
`module type S : sig ... end`