OLD SPRING HARBOR, N.Y., March 23 - Here among the ice-cream parlors, candle shops and heaps of antiques, public toilets have emerged as a threat to all that is quaint.To supporters, installing public bathrooms in this North Shore hamlet in the Town of Huntington would be a panacea to Main Street businesses, a necessary amenity to keep shoppers from being lured to shopping malls, where the discounts are deep and the toilets are plentiful.But in the eyes of a vocal group of residents, the toilets are a menace with a mean flush. They say they will clog traffic on Main...