Associated Press: Car makers are showing off their leanest, greenest mass-market models through Sunday in anticipation of stricter European emissions controls at the Geneva International Motor Show. A host of small cars are celebrating their debut in Geneva, including production versions of Ford Motor Co.’s new, fuel-stingy Fiesta and Toyota Motor Corp.’s three-seater iQ, and a concept version of Fiat’s 500 Aria. All three boast carbon dioxide emissions of under 100 grams per kilometer, which …