The problem the reverted commit tried to fix seems to have been just a
symptom of another root cause that was later fixed as the problem does
not seem to occur anymore even without this changeset also this
changeset broke cabal sandboxes with ghc < 7.8.
Fix#262
This reverts commit 8741323f5b.
Conflicts:
Language/Haskell/GhcMod/GhcPkg.hs
- cradle now stores a list of active package databases instead of only
the user store (if present).
- rename `cradlePackageDb` -> `cradlePkgDbStack` as that`s what the ghc
documentaion calls this kind of thing
- `getPackageDbPackages` now returns names of all visible packages in
the given directory. Also the implementation now uses `ghc-pkg`
instead of manually looking at the package database
