vim (all builds): add licence information

pkgs/applications/editors/vim/macvim.nix

@@ -87,6 +87,7 @@ stdenv.mkDerivation rec {
   meta = with stdenv.lib; {
     description = "Vim - the text editor - for Mac OS X";
     homepage    = https://github.com/b4winckler/macvim;
+    license = with licenses; [ vim ];
     maintainers = with maintainers; [ cstrahan ];
     platforms   = platforms.darwin;
   };