Theater People Celebrate an Institution, Complain About SexLast night was the fifth-anniversary celebration for Angus McIndoe’s, the theater-district hot spot popular before shows with tourists and after shows with actors and critics, and the party drew what one wag identified as the five sectors of the theatergoing population: gays, Jews, gay Jews, the WASPs who write about them, and the women who love them all. Much of the talk was about Spring Awakening, the exhilarating rock musical that opened Sunday night to amazing reviews in yesterday’s papers, and if you’re wondering why the show — about sexual discovery and repression among nineteenth-century teenagers — has struck such a chord with theater critics and reporters, you need only step into their world for a night to learn that this crowd knows more than a little about sexual frustration.