rxvt-unicode-plugins.perls: deprecated plugins

While the clipboard and url-select plugins have been deprecated, it's
likely there are still many users expecting them to exist, so continue
to provide them.

https://github.com/muennich/urxvt-perls/blob/master/deprecated/README.md

pkgs/applications/misc/rxvt-unicode-plugins/urxvt-perls/default.nix

@@ -14,6 +14,9 @@ stdenv.mkDerivation rec {
   installPhase = ''
     mkdir -p $out/lib/urxvt/perl
     cp keyboard-select $out/lib/urxvt/perl
+    cp deprecated/clipboard \
+       deprecated/url-select \
+    $out/lib/urxvt/perl
   '';
 
   meta = with stdenv.lib; {