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.
I seem to recall that I tried adding that second wrapper a while ago, but after I did, ghc-mod didn't work any more. Are you sure that wrapping `ghc-modi` really works?