Build cabal-install-0.14.0 with network 2.3.x on GHC 7.4.2 and below.

Fixes <https://github.com/NixOS/nixpkgs/pull/3770>.

pkgs/top-level/haskell-defaults.nix

···
 
   ghc742Prefs = self : super : ghc763Prefs self super // {
     aeson = self.aeson_0_7_0_4.override { blazeBuilder = self.blazeBuilder; };
+    cabalInstall_0_14_0 = super.cabalInstall_0_14_0.override {
+      HTTP = self.HTTP.override { network = self.network_2_3_0_13; };
+      network = self.network_2_3_0_13;
+    };
     extensibleExceptions = null;        # core package in ghc <= 7.4.x
     hackageDb = super.hackageDb.override { Cabal = self.Cabal_1_16_0_3; };
     haddock = self.haddock_2_11_0;