rdesktop: update to version 1.8.2

rdesktop: add meta fields
(cherry picked from commit 6ad299460caccd4c4ab928d7988f7a1f0460fea8)

Conflicts:
	pkgs/applications/networking/remote/rdesktop/default.nix
Merge release 14.04 into backports.

* 'release-14.04' of github.com:NixOS/nixpkgs:
  rdesktop: update to version 1.8.2