WITH CHRISTMAS in Ireland comes a migration of Irish back to the auld sod, along with stories of triumphs and achievements. Twenty years ago, more left than returned to Ireland at Christmas. This week marks the arrival of friends returning to renew friendships. Oftentimes, it's a parade of fashion and conspicuous consumption. But some locals are confreres who share warm anecdotes and good craic. I've noticed something in the pre-Christmas air about 21st century Ireland and I think it's worth considering as a principle of Irish society.