“The Wedding Singer” has found an unexpectedly ardent audience. “The feel-good play, based on the 1998 movie starring Adam Sandler and Drew Barrymore, received a ho-hum from some critics when it opened April 27, but it is a certified smash with the young-and-in-love set who are using the show’s joyful ambience to create their own personal Kodak moments. With the blessing of the show’s managers and promoters, a half-dozen couples have become engaged on stage at the Al Hirschfeld Theater, and women are lining up for the theater’s Bachelorette Box package.”