Islamic State published a video on Sunday threatening Egyptian Christians and showing the last statement of a man it said was responsible for the deadly bombing in December of a Coptic cathedral in Cairo. The masked man in battle-dress, whom the group identified as Abu Abdallah al-Masri, is seen encouraging militants all over the world not to give up and promising Islamists jailed in Egypt they will be freed soon, when the group "liberates" Cairo. President Abdel Fattah al-Sisi had already identified the bomber as a 22-year-old student called Mahmoud Shafik, and it is believed Abu Abdallah al-Masri was his...