Key TakeawaysGap posted second-quarter earnings and revenue above analysts' estimates on higher sales at its Old Navy and Gap stores.The clothing retailer also boosted its outlook for gross margin and operating income.Shares of Gap finished higher Thursday after an early release led to a trading halt.  Gap (GAP) posted better-than-expected results for the second quarter and boosted its guidance on higher sales at its Gap and Old Navy stores. The company reported second-quarter diluted earnings per share (EP ...