Data.Fixed.Fixed constructor

[Ashley Yakeley]

I'm currently working on updating the Data.Fixed module in base. I am 
adding Typeable and Data instances (automatically derived), and several 
new HasResolution types (including one for 10^-2, monetary currencies 
being an obvious Fixed use).

The Fixed type is simply a newtype of Integer. Should I expose its 
MkFixed constructor?

Against:

* MkFixed is not used in numerical calculation, and isn't itself a 
conversion function from Integer (obviously).

* Ratio doesn't expose its constructor.

For:

* It's possible to recreate it anyway.

* There's a Data instance, so morally the constructor is exposed.

-- 
Ashley Yakeley