LOS ANGELES, January2 (Reuters) - R&B and hip-hop artists have appeared in horror films before, but 28-year old singer Trey Songz tackles a brand new incarnation of the "Texas Chainsaw Massacre" franchise with "Texas Chainsaw 3D." The film, which opens in U.S. theaters on Friday, follows a young woman who inherits a lavish, isolated mansion. When she visits it for the first time with her three friends, one of whom is played by Songz, they realize there is horror awaiting them in the basement. ...