Malaysians have a new favourite pastime these days – guessing when Prime Minister Najib Razak will call the next general election. The vote is due by next August but for months the premier, who has full power to decide when it will be held, has blown hot and cold about triggering a snap contest. When called, the vote will be one of the country’s fiercest ever political battles, pitting Najib against Mahathir Mohamad, the country’s 92-year-old former strongman prime minister…