The party in Macau is about to get a little louder, after MGM Resorts International (MGM) said it's gotten the go-ahead from the region's government to build a new $2.5 billion casino, pushing its shares up in heavy volume early Thursday. MGM China, a joint venture between MGM and Pansy Ho, daughter of Macau casino magnate Stanley Ho, said it received approval from China to build a 1,600-room casino hotel resort in the former Portuguese colony.