Core: Turning: right turn goes before oncoming left turn

This rule is a narrow addition to the ordinary turning duty: it only resolves the case where BOTH drivers turn at the same junction at the same time, one to the right and the other, oncoming, to the left. Within that one case, the right-turner always wins, regardless of who was waiting first. As soon as the oncoming driver is not turning but going straight ahead, this is no longer 'right-turn before left-turn' — then the ordinary turning rule from p.110 simply applies: the left-turner gives way to the straight-ahead traffic. The rule applies to 'drivers' in general: an oncoming cyclist or moped rider turning right also goes before the left-turning car.