haskell-language-nix: pull this library in from Hackage

pkgs/development/haskell-modules/configuration-common.nix

@@ -757,7 +757,6 @@ self: super: {
   # Override the obsolete version from Hackage with our more up-to-date copy.
   cabal2nix = self.callPackage ../tools/haskell/cabal2nix/cabal2nix.nix {};
   hackage2nix = self.callPackage ../tools/haskell/cabal2nix/hackage2nix.nix {};
-  language-nix = self.callPackage ../tools/haskell/cabal2nix/language-nix.nix {};
   distribution-nixpkgs = self.callPackage ../tools/haskell/cabal2nix/distribution-nixpkgs.nix {};
 
   # https://github.com/urs-of-the-backwoods/HGamer3D/issues/7

pkgs/development/tools/haskell/cabal2nix/language-nix.nix

@@ -1,25 +0,0 @@
-{ mkDerivation, base, deepseq, doctest, fetchFromGitHub, lens
-, pretty, QuickCheck, regex-posix, stdenv
-}:
-
-mkDerivation rec {
-  pname = "language-nix";
-  version = "20150903";
-  src = fetchFromGitHub {
-    owner = "nixos";
-    repo = "cabal2nix";
-    rev = "v${version}";
-    sha256 = "1cniaymgwz96bjchan49jv627wjbymc3vs48w1p19qj2k9rly6q7";
-  };
-  postUnpack = "sourceRoot+=/${pname}";
-  libraryHaskellDepends = [
-    base deepseq doctest lens pretty QuickCheck regex-posix
-  ];
-  testHaskellDepends = [
-    base deepseq doctest lens pretty QuickCheck regex-posix
-  ];
-  homepage = "https://github.com/nixos/cabal2nix#readme";
-  description = "Data types and useful functions to represent and manipulate the Nix language";
-  license = stdenv.lib.licenses.bsd3;
-  maintainers = with stdenv.lib.maintainers; [ simons ];
-}