Minnesota hog farmers are wondering when a price slump which has made their pigs almost worthless will end. Prices fell sharply again yesterday as an oversupply of hogs continues to drive the market down. More than 300 producers voiced anger at their precarious economic situation last night in Marshall, during a meeting organized by congressman David Minge. Mainstreet Radio's Mark Steil reports: The collapse of the hog market is the crisis of a lifetime for pork producers. the worst slump they've ever experienced. The Mar