Used by the routines at arch_nudge_loop and handle_exit_screen.

Jumps to the entry in the table of four addresses at BC chosen by the facing of the object at IX, in the order W, E, N, S. Used for the player's step (walk_step_tbl), for leaving a room (screen_move_tbl), and by the archways (arch_nudge_loop), which have facings of their own.