KALMA, Sudan — In Sudan’s sprawling Kalma camp for the displaced, Ansaf Omar lives with the gut-wrenching guilt of losing her toddler to a food crisis that has hit millions of people nationwide.“I am severely malnourished so I couldn’t breastfeed him,” said Omar, 34, a month after her one-and-half-year-old child died in Kalma camp just outside Nyala, the provincial capital of