An internal memo circulated yesterday to St. Louis Post-Dispatch employees indicates that some of the staffers who were laid off could get their jobs back if others resign or retire by January 21.The Post offered a similar deal when it let go of people last fall, and reporters Christine Byers and Patrick M. O'Connell were both able to be "rehired."Yesterday's memo, penned by Arnie Robbins and Pam Maples, the local daily's executive editor and managing editor, respectively, also notes that severa