Add a version of Zen kernel with Con Kolivas' BFS scheduler

svn path=/nixpkgs/trunk/; revision=17142

pkgs/os-specific/linux/zen-kernel/2.6.31-zen0.nix

@@ -62,7 +62,12 @@ in
     killOption CONFIG_ACPI_CUSTOM_DSDT_INITRD
     killOption CONFIG_DEVTMPFS
     killOption CONFIG_DEVTMPFS_MOUNT
-
+  '' +
+  (if a.lib.attrByPath ["ckSched"] false a then ''
+    killOption CONFIG_CPU_CFS
+    setOptionYes CONFIG_CPU_BFS
+  ''else "") +
+  ''
     cp .config ${config}
   '';
 })

pkgs/top-level/all-packages.nix

@@ -5331,6 +5331,10 @@ let
       lib builderDefs;
   };
 
+  kernel_2_6_31_zen0_bfs = kernel_2_6_31_zen0.override {
+    ckSched = true;
+  };
+
   /* Kernel modules are inherently tied to a specific kernel.  So
      rather than provide specific instances of those packages for a
      specific kernel, we have a function that builds those packages