NewMarket Corp. develops and produces additives that are blended into motor oils, automatic transmission fluids and gasoline. As a maker of specialty chemicals, its fortunes hinge on the price of its raw materials and the prices it can get from its own customers. For the past few months, NewMarket (NEU) has enjoyed a middleman's holiday. Its own raw-material costs plunged. But it was able to raise prices to its customers. A company that had often