Add LTS Haskell 3.20.

Changed files
+3
pkgs
+3
pkgs/top-level/haskell-packages.nix
···
lts-3_19 = packages.ghc7102.override {
packageSetConfig = callPackage ../development/haskell-modules/configuration-lts-3.19.nix { };
};
+
lts-3_20 = packages.ghc7102.override {
+
packageSetConfig = callPackage ../development/haskell-modules/configuration-lts-3.20.nix { };
+
};
};
}