* Wall Street ends lower; MSCI world index also down * Downbeat German Ifo survey weighs on euro, European shares * Amazon.com, Visa down after disappointing results (Updates with U.S. market closing levels) By Caroline Valetkevitch NEW YORK, July 25 (Reuters) - Some disappointing U.S. earnings, including Amazon.com, and weak German economic data pressured world stock markets on Friday, while the euro hit an eight-month low against the U.S. dollar. Amazon was the biggest dr