MEXICO CITY (AP) - Hundreds of people lined up at Mexico City's main post office on Friday, some waiting hours to buy postage stamps featuring a black comic book character that U.S. leaders have called racist. The series of five stamps released Wednesday depicts the Memin Pinguin character, a hapless boy drawn with exaggerated features, thick lips and wide-open eyes. His appearance, speech and mannerisms are the subject of kidding by white characters in the comic book, which started in the 1940s and is still published in Mexico. The stamps have become a symbol of resentment that the United States...