NASHVILLE, Tenn. — Country giant Merle Haggard, who rose from poverty and prison to international fame through his songs about outlaws, underdogs and an abiding sense of national pride in such hits as “Okie From Muskogee” and “Sing Me Back Home,” died Wednesday at 79, on his birthday. Haggard’s manager, Frank Mull, said the country icon died in Palo Cedro, California, of pneumonia that he had been battling for months.