Update submodules: plugins (new commits)

plugins:
    df57d9f Greg Holmes <greg@dmdirc.com>
            DI the DNS Plugin (and fix DCOP)

            Gerrit: http://gerrit.dmdirc.com/3182

Change-Id: Ie28578026a7ed0c94953997823f9ead54ea97d3f

modules/plugins

@@ -1 +1 @@
-Subproject commit 539596bc1330ee9729e6750ec14dd50ee1c321bd
+Subproject commit df57d9fff622e2ef1ca185fcab24a5b3e22f9a40