PORTUMNA, Ireland — The myths fade almost as soon as you land on the Emerald Isle. No one greets you in Ireland with “top of the morning.” Corned beef isn’t the national dish. It’s not eaten here at all, St. Patrick’s Day or not. Despite the stereotype fueled by film star Maureen O’Hara — a Dublin native — only 10 percent of Irish are redheads, known as gingers. And travel in Northern Ireland is quite safe, even on the streets of Derry, where 14 unarmed men and teenage boys were shot to death by members of the British Army on …