Sync OpenBSD patchset 1035:

Add move-pane command (like join-pane but allows the same window). Also
-b flag to join-pane and move-pane to place the pane to the left or
above. From George Nachman.

cmd.c

@@ -67,6 +67,7 @@ const struct cmd_entry *cmd_table[] = {
 	&cmd_lock_client_entry,
 	&cmd_lock_server_entry,
 	&cmd_lock_session_entry,
+	&cmd_move_pane_entry,
 	&cmd_move_window_entry,
 	&cmd_new_session_entry,
 	&cmd_new_window_entry,