Add base dependency for data-default-class

[TeofilC]

The next version of GHC requires a dependency on base if any built-ins are used. This package won't compile without adding this dependency.

[TeofilC]

See DanBurton/composition#6 for a similar PR for another package that didn't have a base dependency

[mauke]

I think I'll wait for the next ghc to be released so I can test whether this change really is necessary (and sufficient).

In particular, I think @simonpj is being silly here:

Ah! But you can't know that it "uses no known names"! Suppose GHC desugared f x as (apply f x) where apply is a library function. (Scala does this -- you can overload function application.) Then apply is precisely a known name.

In my case we're talking about an empty module. (Well, mostly empty: It does import/export things, but it contains no declarations.) If GHC needs to inject additional names to implement nothing at all, that seems more like an issue with GHC.

[TeofilC]

FWIW it should be possible to test this using your current CI setup, since I think haskell-ci supports testing against unreleased GHCs/head.hackage. Of course I can understand wanting to wait.

I have also added a patch to head.hackage with this change.