NEW YORK – Hidden in the attention being paid to David Letterman leading to his May 20 retirement is the knowledge that it will also mean the end of a regular television role for America's bandleader, Paul Shaffer. The gravel-voiced sidekick, who's 65, isn't ready to leave show business even with the gig of a lifetime coming to a close after 33 years. "Of course, I had the old mixed feelings, sadness, etcetera," Shaffer said during an interview in his office behind the Ed Sullivan Theater. "Now I have come around to just being absolutely thankful for such a wonderful...