Make `Status` a bit more safe and signature friendly

I love simplicity and efficiency of the current `Status` representation. I wonder if we want to add a tiny layer of typing around it (so we have readable signatures):

```purescript

foreign import data Status :: Type

toInt :: Status -> Into
toInt = unsafeCoerce

continue :: Status
continue = unsafeCoerce 100

ok :: Status
ok = unsafeCoerce 200

...
```