NOISIEL, France — An American mashup artist let passers-by put words in giant zombies’ mouths last week. The show, called Txt of the Living Dead, projected 15-foot-wide, black-and-white stills from George A. Romero’s classic 1968 horror flick Night of the Living Dead onto buildings. Text messages from random people on the street then filled comics-style speech balloons that were added to the images in what New York artist Paul Notzold called an “SMS-enabled interactive street performance.”