complex ruleset parameters

1eaf02f3c30db9ecb5a14b7abe95902a0a8bffc7 has requested the ability to iterate over complex types in ruleset parameters. I.e.

```murphi
type
  t: record
    x: boolean;
  end;

...

ruleset y: t do
...
```

I haven't decided whether this makes sense yet or not.