Revert "Merge branch 'improved-make-overridable' of git://github.com/ElvishJerricco/nixpkgs"

This reverts commit c3af1210b4, reversing
changes made to 49f175cd0c.

pkgs/development/idris-modules/default.nix

@@ -1,8 +1,17 @@
 { pkgs, idris, overrides ? (self: super: {}) }: let
   inherit (pkgs.lib) callPackageWith fix' extends;
 
+  /* Taken from haskell-modules/default.nix, should probably abstract this away */
+  callPackageWithScope = scope: drv: args: (callPackageWith scope drv args) // {
+    overrideScope = f: callPackageWithScope (mkScope (fix' (extends f scope.__unfix__))) drv args;
+  };
+
+  mkScope = scope : pkgs // pkgs.xorg // pkgs.gnome2 // scope;
+
   idrisPackages = self: let
-    callPackage = callPackageWith (pkgs // pkgs.xorg // pkgs.gnome2 // self);
+    defaultScope = mkScope self;
+
+    callPackage = callPackageWithScope defaultScope;
 
     builtins_ = pkgs.lib.mapAttrs self.build-builtin-package {
       prelude = [];