Fix XEP-0078 using the new stream feature workflow.

Honestly, this is mainly just a demo/proof of concept that we
can handle dependencies and ordering issues with stream features.

DON'T use XEP-0078 if you are able to use the normal SASL method,
which should be the case unless you are dealing with a very old
XMPP server implementation.

sleekxmpp/plugins/xep_0078/stanza.py

@@ -0,0 +1,43 @@
+"""
+    SleekXMPP: The Sleek XMPP Library
+    Copyright (C) 2011 Nathanael C. Fritz
+    This file is part of SleekXMPP.
+
+    See the file LICENSE for copying permission.
+"""
+
+from sleekxmpp.xmlstream import ElementBase, ET, register_stanza_plugin
+
+
+class IqAuth(ElementBase):
+    namespace = 'jabber:iq:auth'
+    name = 'query'
+    plugin_attrib = 'auth'
+    interfaces = set(('fields', 'username', 'password', 'resource', 'digest'))
+    sub_interfaces = set(('username', 'password', 'resource', 'digest'))
+    plugin_tag_map = {}
+    plugin_attrib_map = {}
+
+    def get_fields(self):
+        fields = set()
+        for field in self.sub_interfaces:
+            if self.xml.find('{%s}%s' % (self.namespace, field)) is not None:
+                fields.add(field)
+        return fields
+
+    def set_resource(self, value):
+        self._set_sub_text('resource', value, keep=True)
+
+    def set_password(self, value):
+        self._set_sub_text('password', value, keep=True)
+
+
+class AuthFeature(ElementBase):
+    namespace = 'http://jabber.org/features/iq-auth'
+    name = 'auth'
+    plugin_attrib = 'auth'
+    interfaces = set()
+    plugin_tag_map = {}
+    plugin_attrib_map = {}
+
+