Updating go, and making the go expression work in both i686-linux and x86_64-linux.

svn path=/nixpkgs/trunk/; revision=22230

pkgs/build-support/fetchhg/default.nix

@@ -1,17 +1,17 @@
-{stdenv, mercurial, nix}: {url, tag ? null, md5}:
+{stdenv, mercurial, nix}: {name ? null, url, tag ? null, md5 ? null, sha256 ? null}:
 
 # TODO: statically check if mercurial as the https support if the url starts woth https.
 stdenv.mkDerivation {
-  name = "fetchhg";
+  name = "fetchhg" + (if (name != null) then "-${name}" else "");
   builder = ./builder.sh;
   buildInputs = [mercurial nix];
 
   # Nix <= 0.7 compatibility.
   id = md5;
 
-  outputHashAlgo = "md5";
+  outputHashAlgo = if (md5 != null) then "md5" else "sha256";
   outputHashMode = "recursive";
-  outputHash = md5;
+  outputHash = if (md5 != null) then md5 else sha256;
   
   inherit url tag;
 }