Just the phrase ''identical-twin gynecologists'' is kind of chilling. Then add ''a psychological horror movie by David Cronenberg.'' Obviously this is a job for Jeremy Irons, master of the highbrow kinky. Irons maintains cool control of the brothers' two different patterns of disintegration while wielding frightfest gynecological tools to create the most disturbing twins you'll ever see. A
Playing both halves of a male-female twin set in ''Jack and Jill,'' Adam Sandler joins a long list of actors in dual roles. Lisa Schwarzbaum grades past two-roles-for-one-actor deals