Make the jit accept an EqualityComparer<Input>

[gafter]

Since the jit should only "care about" changes to inputs that are significant for the function being jitted, you may want to use a custom equals and hashCode implementation for the jit. In order to permit that, the jit should take an optional parameter of the interface type EqualityComparer<Input>... but unfortunately such a type doesn't appear to exist in the Kotlin (or Java) APIs.