add Storable a => Storable (Ratio a) and Storable a => Storable (Complex a) to base

[Henning Thielemann]

On Mon, 3 Nov 2014, Henning Thielemann wrote:

> On Mon, 3 Nov 2014, Edward Kmett wrote:
>
>> +1 from me. Storable (Ratio a) probably won't see much use, but it should 
>> exist nonetheless to prevent it
>> having to be orphaned.
>
> Omitting the Ratio instance it has the advantage that people are warned.

We could also block such an instance:
   https://ghc.haskell.org/trac/ghc/ticket/7775
   https://ghc.haskell.org/trac/ghc/ticket/9334