mix.exs: Update 'xmpp' and 'stun'

mix.exs

@@ -85,12 +85,12 @@ defmodule Ejabberd.Mixfile do
     [{:lager, "~> 3.6.0"},
      {:p1_utils, "~> 1.0"},
      {:fast_xml, "~> 1.1"},
-     {:xmpp, "~> 1.4"},
+     {:xmpp, git: "https://github.com/processone/xmpp", ref: "f8c5b3bb"},
      {:cache_tab, "~> 1.0"},
      {:stringprep, "~> 1.0"},
      {:fast_yaml, "~> 1.0"},
      {:fast_tls, "~> 1.1"},
-     {:stun, "~> 1.0"},
+     {:stun, git: "https://github.com/processone/stun", ref: "f1516827", override: true},
      {:esip, "~> 1.0"},
      {:p1_mysql, "~> 1.0"},
      {:mqtree, "~> 1.0"},