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.c

@@ -198,6 +198,7 @@ win_create_muc(const char *const roomjid)
     new_win->enctext = NULL;
     new_win->message_char = NULL;
     new_win->is_omemo = FALSE;
+    new_win->sent_messages = g_hash_table_new_full(g_str_hash, g_str_equal, free, NULL);
 
     new_win->memcheck = PROFMUCWIN_MEMCHECK;