is the orphans module necessary?

[symbiont-sam-halliday]

I am wondering why Aeson and QuickCheck instances are in a separate module instead of enabled via CPP, is there a design reason for the current layout?

e.g. it is possible to guard blocks of code that import and define the instances like so (here using transformers as an example, but equally applicable to Aeson / QuickCheck)

#ifdef VERSION_transformers
import           Control.Monad.Trans.Class (MonadTrans, lift)
#endif

https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/phases.html#standard-cpp-macros or define your own constant.

Would you welcome a PR removing the orphan modules and using CPP like this?

[chessai]

resolved in e9466fb