Mortgage finance giant Fannie Mae, helped by the U.S. housing market's continued recovery, posted an $17.2 billion US annual profit for 2012 on Tuesday, its largest ever yearly gain and its first in six years.Fannie Mae and its smaller sibling company Freddie Mac are returning to health as home prices have leveled off and mortgage delinquencies have dampened. Last month, Freddie posted an $11 ...