In Shirt-Sleeve Holiday Season, Overcoats Linger on the Racks
Balmy temperatures on East Coast, with average highs this holiday season 15 degrees warmer than last year, have been disastrous for sales of all kinds of cold-weather clothing; glut of winter wear has sent chill through executive suites of major retailers, who count on big profits from coats in crucial holiday shopping season; they are even starting to grumble about first 'global warming Christmas'; photos (M)