NEW YORK — A quick-thinking Manhattan homeless man likely saved his own life when he scared off a gunman who shot him by pretending to call 911 — despite not having a phone. The gunman went on to shoot another sleeping homeless man to death just an hour later, and now police are offering a $10,000 reward for information leading to his arrest. The surviving victim, a 38-year-old man, was sleeping on King Street in Hudson Square when he awoke to the sensation of a bullet tearing through his right forearm about 5 a.m. Saturday, cops said. “What are you doing?” he screamed when he saw the shooter,…