pre-710 compatibility stuff

[lennart spitzner]

On 24/10/15 15:05, Thomas Tuegel wrote:
> MIN_VERSION_base is defined by Cabal, so it is not available during
> bootstrapping. This means we unfortunately need to use
> __GLASGOW_HASKELL__ in Cabal, even though it isn't really the right
> macro. It should be safe to use MIN_VERSION_base in cabal-install.

ok, that makes sense, thanks Thomas and Herbert.

Herbert also mentioned the qualified import trick to avoid CPP (the
"more robust way" on [1]). While it is nifty, i am reluctant to apply
it, given the silent/implicit requirement to have at least one
reference to the qualified entity. Every contributor to such a module
must be aware of this trick or risk accidentally breaking it. The
explicitness of CPP seems preferable to me.

[1]
https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10#GHCsaysTheimportof...isredundant