Agence France-Presse: Leaders of the world’s richest nations Monday opened a summit aimed at battling skyrocketing oil and food prices, as pressure mounted on them to live up to their pledges to help Africa. Leaders including US President George W. Bush gathered in the secluded spa resort of Toyako in northern Japan for a three-day session, with seven African leaders joining them on the first day to take up the plight of the continent. Riot police with shields stood under pouring rain and blocked …