Used by the routines at upd_22, upd_63, upd_23 and set_deadly_wipe_and_draw_flags.

Sets bits 7 and 5 of +13. The collision code (adj_for_out_of_bounds) passes bit 7 of a moving object on to whatever it runs into, and bit 5 of an object on to whatever runs into it, as bit 6 -- the "has touched something deadly" flag the player's handler checks. With both set, it does not matter who moved.