advice on minor cleanups?

All, It appears that `runHscBackendPhase` returns a tuple that include an element of type `Maybe Linkable` but that in practice is always `Nothing`. I'm thinking of removing this element from the tuple, which would also entail simplifying the type of value constructor `T_HscBackend` for the `TPhase` type. Simplifying the code seems like a good thing, but perhaps there is a reason to leave well enough alone? Please advise me. Norman