Gu Kailai, the wife of the disgraced political leader Bo Xilai, has been indicted for intentional homicide, in a crime that has triggered China’s most serious political crisis in decades. The official Xinhua news agency on Thursday evening published a brief dispatch announcing that Ms. Gu and an aide employed by the family had been formally charged in the poisoning death of the Briton, Neil Heywood, 41, whose body was found last November in a hotel in Chongqing, the sprawling municipality Mr. Bo led until his downfall.