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

[Henning Thielemann]

On Mon, 3 Nov 2014, Edward Kmett wrote:

> Haskell as a language and GHC as an implementation both lack a mechanism for 'explicitly forbidding the
> construction of an instance'.

In the links I sent, it is described how to achieve that with current 
available technology:
    https://ghc.haskell.org/trac/ghc/ticket/9334#comment:9


> The badness of the abstraction, however, is not helped nor harmed by the existence of a Storable instance.

My point was, that Storable means "fixed size type", and thus it selects 
the inappropriate types from the Integral ones. As I said, there could be 
other big integer types where Ratio works, but they won't be Storable.