A homeless man told the police on Friday that his conscience drove him to reveal something he’d kept secret — that he’d beaten a man to death in South Providence 24 years ago. By nightfall, Daniel Serrano, 65, was charged with the murder of 32-year-old Michael Holliday — a man he said he didn’t intend to kill, Maj. David Lapatin said. “He claims he was feeling very guilty about it,” the police major added. A workman discovered Holliday’s body in a vacant third-floor apartment at 27 Somerset St. on Feb. 24, 1990. The man had been beaten to death. He...