HAVANA (Reuters) - North Korea gave Cuba extensive military support in the 1980s, former President Fidel Castro said on Wednesday as the United Nations investigated a cargo of hidden Cuban arms discovered last month in the hold of a North Korean ship. Castro, who turned 87 on Tuesday and is rarely seen or heard from in public these days, gave his people a lengthy glimpse of his thoughts in a column dated Tuesday and run in all official media on Wednesday. Topics included the origin of man, relations with the Soviet Union, the assassination of U.S. ...