Four years ago in Fort Worth, Texas, Marin Alsop was seen wiping away tears as an 18-year-old Lim Yunchan finished Rachmaninoff’s Piano Concerto No. 3 in the final round of the Van Cliburn International Piano Competition. On Sunday at the Seoul Arts Center, the two returned to the same concerto, this time with the Philadelphia Orchestra, and the audience rose to its feet, drawing an encore of Elgar’s “Salut d’amour” from Lim. Korean poet Chung Hyun-jong once wrote that when a person comes to you