In a spare, powerful text and evocative illustrations, the Newbery medalist Katherine Applegate and the artist G. Brian Karas present the extraordinary real story of a special gorilla.     Captured as a baby, Ivan was brought to a Tacoma, Washington, mall to attract shoppers. Gradually, public pressure built until a better way of life for Ivan was found at Zoo Atlanta. From the Congo to America, and from a local business attraction to a national symbol of animal welfare, Ivan the Shopping Mall Gorilla traveled an astonishing distance in miles and in impact.     This is his true story and includes photographs of Ivan in the back matter.