Add version attribute where maintainers |= nckx

This will probably be mandatory soon, and is a step in the right
direction. Removes the deprecated meta.version, and move some meta
sections to the end of the file where I should have put them in
the first place.

pkgs/tools/package-management/dpkg/default.nix

@@ -1,9 +1,8 @@
 { stdenv, fetchurl, perl, zlib, bzip2, xz, makeWrapper }:
 
-let version = "1.18.4"; in
-
-stdenv.mkDerivation {
+stdenv.mkDerivation rec {
   name = "dpkg-${version}";
+  version = "1.18.4";
 
   src = fetchurl {
     url = "mirror://debian/pool/main/d/dpkg/dpkg_${version}.tar.xz";