Call it a ’21’ Big Guns Salute. Iraq war Marine hero Aaron Mankin surprised a Veterans Day fund-raiser honoring Oscar hopeful “The Hurt Locker.” “Sorry to interrupt your lunch, but you already interrupted mine,” the jovial corporal quipped. Mankin was lunching downstairs at ’21’ when Intrepid trustee Gerry Byrne whisked him upstairs. He spoke of his love for his country and a city of strangers who embraced him yesterday. Among the A- listers leaping to a standing ovation were Oliver Stone, Debra Winger, Willem Dafoe, Bob Balaban, “Hurt Locker” star Anthony Mackie, director Kathryn Bigelow, screenwriter Mark Boal and journalists Jeff Greenfield, Dan Abrams and Bill McCuddy.