(05-16) 21:43 PDT CAMBRIDGE, Mass. (AP) -- City clerks began handing out marriage-license applications to gay couples just after midnight Monday, making Massachusetts the first state in the nation to legalize same-sex unions and the United States just one of four countries in the world where homosexuals can legally wed. The first couple to begin filling out the paperwork was Marcia Hams, 56, and her partner, Susan Shepherd, 52, of Cambridge. They showed up a full 24 hours ahead of time to stake out the first spot in line to get the nation's first state-sanctioned gay marriage applications. "I'm shaking...