Robby Ginepri is the first U.S. man to reach the fourth round of the French Open since Andre Agassi in 2003. Ginepri, the last American man or woman playing singles in this year’s tournament, beat Florent Serra of France 6-4, 6-4, 6-4 Saturday. The 88th-ranked Ginepri never had won a match at Roland Garros until this week, losing in the first round in each of his previous five appearances at the…