Wrap Haskell tools to find GHC packages

Several Haskell tools that use GHC are missing the environment wrapping required to find Haskell packages:
* `ghc-mod` was correctly wrapped, but not `ghc-modi`
* `haddock` was wrapped prior to 2.10, but not since then.
`haddock` will refuse to run if the `ghc` it finds at runtime is a different version than it was compiled with, so I don't think this is a problem.