Levi Strauss & Co. originally put that little pocket in the front of its jeans so that miners would have a place to keep their matches. Now the classic design is changing to make way for the ubiquitous iPod. Levi's DLX jeans, to be introduced in the fall, will have a trackpad permanently mounted on top of the pocket and a socket. Levi's is being coy about the new product--it hasn't released any pictures yet. The company insists the jeans are washable--provided you take out the iPod first.