Reduce the size of the Nixpkgs/NixOS jobsets

This cuts nixpkgs:trunk from 78K to 31K jobs by disabling builds of
{node,go,python,emacs,coq,r,ocaml,perl}Packages. Thus these are now
only built if they are dependencies of top-level packages (such as
end-user applications). I left haskellPackages because they take
typically longer to build than the others (which are mostly
interpreted languages), so disabling them would be more painful to
users.

This is a temporary measure until we have a binary cache based Hydra
running on faster hardware, necessitated by the fact that evaluations
now regularly time out after 6 hours.

pkgs/top-level/all-packages.nix

···
 
   nodePackages_5_x = callPackage ./node-packages.nix { self = nodePackages_5_x; nodejs = nodejs-5_x; };
 
-  nodePackages_4_x = recurseIntoAttrs (callPackage ./node-packages.nix { self = nodePackages_4_x; nodejs = nodejs-4_x; });
+  nodePackages_4_x = callPackage ./node-packages.nix { self = nodePackages_4_x; nodejs = nodejs-4_x; };
 
   nodePackages_0_10 = callPackage ./node-packages.nix { self = nodePackages_0_10; nodejs = nodejs-0_10; };
 
···
 
   ### DEVELOPMENT / GO MODULES
 
-  go14Packages = recurseIntoAttrs (callPackage ./go-packages.nix {
+  go14Packages = callPackage ./go-packages.nix {
     go = go_1_4;
     buildGoPackage = callPackage ../development/go-modules/generic {
       go = go_1_4;
       govers = go14Packages.govers.bin;
     };
     overrides = (config.goPackageOverrides or (p: {})) pkgs;
-  });
+  };
 
-  go15Packages = recurseIntoAttrs (callPackage ./go-packages.nix {
+  go15Packages = callPackage ./go-packages.nix {
     go = go_1_5;
     buildGoPackage = callPackage ../development/go-modules/generic {
       go = go_1_5;
       govers = go15Packages.govers.bin;
     };
     overrides = (config.goPackageOverrides or (p: {})) pkgs;
-  });
+  };
 
   goPackages = go15Packages;
 
···
     self = python33Packages;
   };
 
-  python34Packages = recurseIntoAttrs (callPackage ./python-packages.nix {
+  python34Packages = callPackage ./python-packages.nix {
     python = python34;
     self = python34Packages;
-  });
+  };
 
   python35Packages = recurseIntoAttrs (callPackage ./python-packages.nix {
     python = python35;
     self = python35Packages;
   });
 
-  pypyPackages = recurseIntoAttrs (callPackage ./python-packages.nix {
+  pypyPackages = callPackage ./python-packages.nix {
     python = pypy;
     self = pypyPackages;
-  });
+  };
 
   bsddb3 = pythonPackages.bsddb3;
 
···
     cask = callPackage ../applications/editors/emacs-modes/cask { };
   };
 
-  emacs24Packages = recurseIntoAttrs (emacsPackagesGen emacs24 pkgs.emacs24Packages);
+  emacs24Packages = emacsPackagesGen emacs24 pkgs.emacs24Packages;
 
   emacsPackagesNgGen = emacs: import ./emacs-packages.nix {
     overrides = (config.emacsPackageOverrides or (p: {})) pkgs;
···
 
   };
 
-  coqPackages = recurseIntoAttrs (mkCoqPackages_8_4 coqPackages);
-  coqPackages_8_5 = recurseIntoAttrs (mkCoqPackages_8_5 coqPackages_8_5);
+  coqPackages = mkCoqPackages_8_4 coqPackages;
+  coqPackages_8_5 = mkCoqPackages_8_5 coqPackages_8_5;
 
   cvc3 = callPackage ../applications/science/logic/cvc3 {
     gmp = lib.overrideDerivation gmp (a: { dontDisableStatic = true; });

pkgs/top-level/release.nix

···
       zsh = linux;
       zsnes = ["i686-linux"];
 
-      emacs24PackagesNg = packagePlatforms pkgs.emacs24PackagesNg;
+      #emacs24PackagesNg = packagePlatforms pkgs.emacs24PackagesNg;
 
       gnome = {
         gnome_panel = linux;
···
       haskell.compiler = packagePlatforms pkgs.haskell.compiler;
       haskellPackages = packagePlatforms pkgs.haskellPackages;
 
-      rPackages = packagePlatforms pkgs.rPackages;
+      #rPackages = packagePlatforms pkgs.rPackages;
 
       strategoPackages = {
         sdf = linux;
···
         dryad = linux;
       };
 
-      pythonPackages = {
-        zfec = linux;
-      };
+      ocamlPackages = { };
+
+      perlPackages = { };
+
+      pythonPackages = { };
+      python2Packages = { };
+      python27Packages = { };
+      python3Packages = { };
+      python35Packages = { };
 
       xorg = {
         fontadobe100dpi = linux ++ darwin;