protobuf: Support both 2.5 and 2.6 and make 2.6 the default

pkgs/development/libraries/protobuf/2.5.nix

@@ -0,0 +1,9 @@
+{ callPackage, fetchurl, ... } @ args:
+
+callPackage ./generic.nix (args // rec {
+  version = "2.5.0";
+  src = fetchurl {
+    url = "http://protobuf.googlecode.com/files/${version}.tar.bz2";
+    sha256 = "0xxn9gxhvsgzz2sgmihzf6pf75clr05mqj6218camwrwajpcbgqk";
+  };
+})

pkgs/development/libraries/protobuf/2.6.nix

@@ -0,0 +1,11 @@
+{ callPackage, fetchFromGitHub, ... } @ args:
+
+callPackage ./generic.nix (args // rec {
+  version = "2.6.1";
+  src = fetchFromGitHub {
+    owner = "google";
+    repo = "protobuf";
+    rev = "v${version}";
+    sha256 = "03df8zvx2sry3jz2x4pi3l32qyfqa7w8kj8jdbz30nzy0h7aa070";
+  };
+})

pkgs/development/libraries/protobuf/generic.nix

@@ -1,14 +1,20 @@
-{ fetchurl, stdenv, zlib }:
+{ stdenv, version, src
+, autoreconfHook, zlib, gtest
+, ...
+}:
 
 stdenv.mkDerivation rec {
-  name = "protobuf-2.5.0";
+  name = "protobuf-${version}";
 
-  src = fetchurl {
-    url = "http://protobuf.googlecode.com/files/${name}.tar.bz2";
-    sha256 = "0xxn9gxhvsgzz2sgmihzf6pf75clr05mqj6218camwrwajpcbgqk";
-  };
+  inherit src;
 
-  buildInputs = [ zlib ];
+  postPatch = ''
+    rm -rf gtest
+    cp -r ${gtest.source} gtest
+    chmod -R a+w gtest
+  '';
+
+  buildInputs = [ autoreconfHook zlib ];
 
   doCheck = true;