PARIS (Reuters) - U.S. stock index futures pointed to a higher open on Wall Street on Tuesday, with futures for the S&P 500 up 0.04 percent, Dow Jones futures up 0.07 percent and Nasdaq 100 futures up 0.22 percent at 0933 GMT. European stocks gained ground on Tuesday morning as investors were buoyed by the latest batch of U.S. data and earnings and were hopeful a meeting of European leaders later in the week can advance plans to tackle Spain and Greece's debts. ...