A Walmart worker was charged Wednesday with the brutal 1984 murder and rape of a 16-year-old Long Island girl — ending decades of mystery and speculation, Nassau County prosecutors announced. Richard Bilodeau, 63, was arraigned on murder charges for the Nov. 10, 1984, cold-case slaying of Theresa Fusco, thanks to high-tech DNA testing by the FBI, authorities said. “I never gave up hope,” Thomas Fusco, the slain teen’s dad, told reporters. “I always had faith in the system.