* U.S. economic growth picked up in second quarter * Facebook (NasdaqGS: FB - news) , Whole Foods fall after results * US quarterly earnings over half way through * Dow down 0.08 pct, S&P down 0.07, Nasdaq up 0.34 pct (Updates to afternoon) July 30 (Reuters) - The S&P 500 was on track for its flattest session in two weeks on Thursday as investors digested ho-hum corporate earnings and new data showed that the economy grew more quickly in the second quarter. Procter & Gamble, Facebook and Whole Foods Market all fell after quarterly reports that left investors wanting more. U.S. economic growth accelerated in the June quarter as solid consumer spending offset a drag from weak business spending on equipment, suggesting steady momentum that could bring the Federal Reserve closer to hiking interest rates this year. With... More