EMI: Fix handling of actor turn chores

Three small fixes for the handling of actor turn chores:
 - In EMI's coordinate system positive yaw changes mean right turns. We have to take that into account when animating turns and selecting turn chores.
 - Scripts use set_turn_chores(nil, nil) to reset an actor's turn chores, e.g. when Guybrush picks up the hot coals in wed.lua.
 - When the turn chores are changed mid-turn the old animation is stopped, but the new one is not started until the turn direction changes. Can be easily reproduced by hitting the run key while turning Guybrush.