Rework MUC reflected message filtering

Reflected messages can't be filtered by nick only otherwise you might
ignore messages comming from you on another devices.

Consequently we maintain a list of sent messages id in mucwin.
To be sure the id will be correctly reflected we use the origin-id
stanza.

src/ui/window_list.c

@@ -561,6 +561,7 @@ wins_close_by_num(int i)
                 ProfMucWin *mucwin = (ProfMucWin*)window;
                 autocomplete_remove(wins_ac, mucwin->roomjid);
                 autocomplete_remove(wins_close_ac, mucwin->roomjid);
+                g_hash_table_remove_all(mucwin->sent_messages);
                 break;
             }
             case WIN_PRIVATE: