Just in time for Halloween, it’s Williamsburg’s worst nightmare. We’re told Ralph Lauren’s Double RL & Co will open Friday morning at 85 North 3rd Street, right next to the new Steven Alan Optical store and just around the corner from the new J.Crew store, and the new Urban Outfitters, and the new Madewell, and the new (and now boozed-up!) Starbucks. Soon the neighborhood will be called Williamsburg Mills.