Mark partial functions as such

[Henning Thielemann]

On Fri, 31 Aug 2018, Ryan Trinkle wrote:

> This is probably not really for the libraries list, but in the same vein 
> as this discussion, I think it would be extremely helpful to have a way 
> of banning functions that does *not* require changing the upstream 
> library.  I would be thrilled to have a machine-checked ban on use of 
> the 'head', 'tail', etc.

So far I have HLint rules to ban them. Unfortunately, they do not work 
transitively. People have already proposed a TotalHaskell pragma 
analogously to SafeHaskell.