HAVANA (Reuters) - A group of Cubans making the third bid in two years to reach the United States in a vintage American car converted into a boat were intercepted by the U.S. Coast Guard, relatives said on Wednesday. In their impoverished Havana neighborhood, tearful mothers implored U.S. authorities to allow the emigres to stay in the United States, saying they would be jailed if returned to Communist-run Cuba. Thirteen Cubans, including six children, sailed across the Florida Straits in a 1949 Mercury with an built-on prow and a taxi sign on the roof. They were intercepted about 20 miles...