Use message processing hints in the OTR plugin

plugins/otr.py

@@ -347,6 +347,8 @@ class PoezioContext(Context):
                                          mbody=msg.decode('ascii'),
                                          mtype='chat')
         message.enable('carbon_private')
+        message.enable('no-copy')
+        message.enable('no-permanent-store')
         message.send()
 
     def setState(self, newstate):

src/connection.py

@@ -161,6 +161,7 @@ class Connection(slixmpp.ClientXMPP):
         self.register_plugin('xep_0280')
         self.register_plugin('xep_0297')
         self.register_plugin('xep_0308')
+        self.register_plugin('xep_0334')
         self.init_plugins()
 
     def set_keepalive_values(self, option=None, value=None):