He always had them laughing their heads off. The hero cop who nabbed the killer behind the legendary 1983 New York Post headline “Headless body in topless bar” died Friday after a long, fittingly colorful life. Retired New York City Transit Police Detective Frederick “Freddy” Mack, 79, passed away while in hospice care, his daughter Debbie Comstock told The Post on Sunday. “He was a man full of character,” Comstock, 58, said. “He always had stories and jokes to tell. He was loved by many.” Perhaps Mack’s biggest story of all unfolded in April 1983, after 25-year-old lowlife Charles Dingle...