Sadiq al-Mahdi's political career is one of the longest in modern Sudanese history, including two stints as prime minister.#160; But amid an unprecedented upheaval that has seen mass street protests and a military coup, al-Mahdi says he will step away from partisan politics.#160; With a people-led revolution still rocking Sudan, former prime minister Sadiq al-Mahdi ? the country?s last democratically elected leader ? might be expected to jump back into the political horse race. The 83-year-old leader has a reputation as a political survivor, and returned to Sudan in December from a year in self-imposed exile amid massive anti-government protests. But instead he says it's time for him to...