Strip Nick element in message stanzas sent to a room (#686)

include/ns.hrl

@@ -152,3 +152,4 @@
 -define(NS_CLIENT_STATE,  <<"urn:xmpp:csi:0">>).
 -define(NS_STREAM_MGMT_2,  <<"urn:xmpp:sm:2">>).
 -define(NS_STREAM_MGMT_3,  <<"urn:xmpp:sm:3">>).
+-define(NS_NICK,  <<"http://jabber.org/protocol/nick">>).

src/mod_muc_room.erl

@@ -972,7 +972,8 @@ process_groupchat_message(From,
 			   of
 			 drop ->
 			     {next_state, normal_state, StateData};
-			 NewPacket ->
+			 NewPacket1 ->
+			     NewPacket = xml:remove_subtags(NewPacket1, <<"nick">>, {<<"xmlns">>, ?NS_NICK}),
 			     send_multiple(jlib:jid_replace_resource(StateData#state.jid,
 								     FromNick),
 					   StateData#state.server_host,