Alice Diop is turning the camera inward on the constructs of insanity, motherhood, and infanticide. Diop’s first narrative feature, “Saint Omer,” is France’s official Oscar entry. Named after the northern French town where the film is set, “Saint Omer” is inspired by the harrowing true crime story of mother Fabienne Kabou, accused of killing her 15-month-old daughter by abandoning her to the rising tide on a beach.