John McEnroe made his debut at 18 with a bang.An unseeded upstart, the Queens native found himself on the same clay courts where he was once a ballboy — gliding and grinding in an interborough contest against Brooklyn-born Top Tenner Eddie Dibbs in his third-round match. But, on the first changeover, something wildly unexpected happened.“We were switching sides and then there was some commotion up in the stands, and the umpire said to us, ‘Someone’s been shot in the stands,’ ” McEnroe, 64, told The Post.
