Everyone who attended art-school theory seminars from the mid-1970s on, and everyone who reads Artforum, knows that in 1974, New York artist Lynda Benglis’s gallery purchased two pages of ad space in the magazine’s November issue. That advertisement is the basis for the recent three-gallery exhibition “Benglis 73/74.” Its curator, Geoff Newton, is an artist with a taste for the textual (he sometimes paints covers of art books or magazines). For this show, he assembled works by a long list of British and American artists, from Sarah Lucas and Cosey Fanni Tutti to Robert Mapplethorpe and Benglis