haskell.lib: move lib.nix into same directory as compose.nix

pkgs/development/haskell-modules/lib/default.nix

@@ -9,7 +9,7 @@ rec {
      between the function name and argument of another. haskell.lib.compose is
      preferred for any new code.
   */
-  compose = import ./lib/compose.nix { inherit pkgs lib; };
+  compose = import ./compose.nix { inherit pkgs lib; };
 
   /* This function takes a file like `hackage-packages.nix` and constructs
      a full package set out of that.

pkgs/top-level/haskell-packages.nix

@@ -19,7 +19,7 @@ let
     "ghcHEAD"
   ];
 
-  haskellLibUncomposable = import ../development/haskell-modules/lib.nix {
+  haskellLibUncomposable = import ../development/haskell-modules/lib {
     inherit (pkgs) lib;
     inherit pkgs;
   };