Lauren Bacall and Susan Sarandon will be feted by Boston U. as part of the school’s “Bette Davis Centenary Tribute.”The Sept. 18 event will coincide with the debut of the United States Postal Service’s Bette Davis stamp and the opening of the university’s exhibition on the actress’s life and career. The awards are being presented by the Bette Davis Foundation and will be given to the actresses at a tribute hosted by film critic Rex Reed. Sarandon will be receiving the Bette Davis Lifetime Achievement Award while Bacall will be honored with the Bette Davis Medal of Honor. Davis, the two-time Oscar winner who died in 1989, was a native of Lowell, Mass. Her papers are housed at Boston U.’s Howard Gotlieb Archival Research Center, which is co-sponsoring the centenary event.