Nigeria's Buhari warns off separatists, takes back control after treatment

By Felix OnuahABUJA (Reuters) - Nigeria's President Muhammadu Buhari said on Monday he would stop separatist activists spreading unrest, seeking to reassert his hold on power after returning from his second stint of medical leave this year.Buhari, looking thin but sounding stronger than his last broadcast in June, said he had been troubled by social media posts calling for splits in a country made up of a mostly Muslim north and a Christian south.Since Buhari traveled to London for treatment of