South Korea's five automakers, led by Hyundai Motor Co, said that their sales increased 9.9% YoY in July 2011 thanks mainly to overall gains in demand at home and abroad. Their combined sales came to 626,060 units in July 2011 as compared with the 570,062 vehicles a year earlier. Sales in overseas markets gained 10.9% YoY to 498,823 units in July 2011 while domestic shipments rose by 6.2% YoY to 127,237…