MALIBU, Calif. — Officials in Southern California reported significant overnight growth of a wind-driven wildfire that has forced thousands of people, including celebrities like Cher and Dick Van Dyke, from their homes in Malibu, but forecasters said firefighters would get a break from improving weather conditions. With much of the coastal city under evacuation orders and warnings, residents waited anxiously to see whether their properties had been spared by the fire, which erupted late Monday and grew to more than 6 square miles (16 square kilometers) by Wednesday morning.