Moving all CPP stuff (that depends on GHC version) to Gap

- Moved some functions from Language.Haskell.GhcMod.Doc to Gap
- Moved HasType typeclass and some functions from Info to Gap
- Adjusted all the other modules to use necessary functions from Gap
  instead of the functions from modified modules

Language/Haskell/GhcMod/Browse.hs

@@ -7,6 +7,7 @@ import Data.Maybe (fromMaybe)
 import DataCon (dataConRepType)
 import GHC
 import Language.Haskell.GhcMod.Doc
+import qualified Language.Haskell.GhcMod.Gap as Gap
 import Language.Haskell.GhcMod.GHCApi
 import Language.Haskell.GhcMod.Types
 import Name
@@ -102,4 +103,4 @@ removeForAlls' ty (Just (pre, ftype))
     | otherwise           = ty
 
 showOutputable :: Outputable a => DynFlags -> a -> String
-showOutputable dflag = unwords . lines . showUnqualifiedPage dflag . ppr
+showOutputable dflag = unwords . lines . Gap.showUnqualifiedPage dflag . ppr