On a bright recent morning, Van Thomas was holding forth from his front porch in Central Los Angeles, alongside his mixed-breed dog, Princess.  “I’ve been a part of this neighborhood for 45 years,” he said. “I grew up playing ball across the street.”  Thomas has seen a world of change sweep through the area over the years, the latest occurring in a small, century-old complex of buildings right next door. A health-care center is opening there for as many as 62 people newly released from the hospital, all of them homeless, many of them struggling to recover from drug addiction.