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/ErrMsg.hs

@@ -73,7 +73,7 @@ ppMsg spn sev dflag msg = prefix ++ cts ++ "\0"
 ----------------------------------------------------------------
 
 showMsg :: DynFlags -> SDoc -> String
-showMsg dflag sdoc = map toNull $ showUnqualifiedPage dflag sdoc
+showMsg dflag sdoc = map toNull $ Gap.showUnqualifiedPage dflag sdoc
   where
     toNull '\n' = '\0'
     toNull x = x