Added "python-$version-wrapper" expression.

The python wrapper expression expects a list of Python modules, $extraLibs,
which are added to $PYTHONPATH before executing the actual Python interpreter.

svn path=/nixpkgs/trunk/; revision=23194

pkgs/development/interpreters/python/2.7/default.nix

@@ -47,6 +47,7 @@ in
 
 stdenv.mkDerivation ( {
   name = "python-${version}";
+  inherit majorVersion version;
 
   src = fetchurl {
     url = "http://www.python.org/ftp/python/${version}/Python-${version}.tar.bz2";