REPOSITIONING? Two more advertising oddities. McDonald's has re-issued the Big Mac slogan (two all beef patties special sauce lettuce cheese pickle onion on a sesame seed bun -- at one time rattling that off at a stand was good for a coupon) as a hip-hop number. A company called J. G. Wentworth, which appears to be a payday loan business with practice restricted to structured settlements and annuities, has been soliciting business using a bargain counter-tenor and mezzo-soprano in best oratorio fashion. Go figure.