NEW YORK — Retailers reported dismal sales figures for December on Thursday as even Wal-Mart Stores Inc., one of the bright spots in the industry, finally buckled under the pressures of the deteriorating economy. As the figures confirmed fears that the holiday season was the weakest in four decades, the malaise cut through practically all areas from kitchen gadget stores to jewelry purveyors and teen apparel retailers. The deep discounts that began well before the official start of the holiday season spurred a number of merchants to cut their earnings outlooks, fueling more concerns about the