Ignore hints when checking for chat states

Ignore XEP-0334 elements when checking whether a stanza is a stand-alone
XEP-0085 chat state notification.  This allows for CSI-filtering chat
states with (e.g.) a no-store hint.

Thanks to Thilo Molitor for reporting the issue.

src/misc.erl

@@ -195,7 +195,7 @@ get_mucsub_event_type(_Packet) ->
 is_standalone_chat_state(Stanza) ->
     case unwrap_carbon(Stanza) of
 	#message{body = [], subject = [], sub_els = Els} ->
-	    IgnoreNS = [?NS_CHATSTATES, ?NS_DELAY, ?NS_EVENT],
+	    IgnoreNS = [?NS_CHATSTATES, ?NS_DELAY, ?NS_EVENT, ?NS_HINTS],
 	    Stripped = [El || El <- Els,
 			      not lists:member(xmpp:get_ns(El), IgnoreNS)],
 	    Stripped == [];