The home improvement retailer is still facing a serious economic headwind.With nothing more than a quick glance at last quarter's core numbers, shares of Lowe's (LOW -3.57%) should be higher today. Sales as well as earnings were better than expected. Dig deeper, though. Not only were the retailer's revenue and per-share profits down year over year, but the company reported its stores are still suffering shrinking sales, with no real relief in sight. The results were bad enough to leave Lowe's stock down 4% ...