If you build it, he will come." Huh? Kevin Costner is hearing voices. The Bull Durham stud is playing a foursquare Iowa farmer this time. He's the kind of average Joe that Jimmy Stewart embodied in such vintage Frank Capra corn as Mr. Smith Goes to Washington and It's a Wonderful Life. In Field of Dreams, adapted by director Phil Alden Robinson from the 1982 W.P. Kinsella novel Shoeless Joe, Costner is homebody Ray Kinsella. That's his wife, an endearingly feisty Amy Madigan, and his daughter,…