LONDON (Reuters) - European shares fell for a second straight day and the euro slid on Thursday, as weak German retail sales and poor earnings at its biggest bank added to investors' nerves after a shock fourth quarter contraction in the U.S. economy. Data on Wednesday showed U.S. GDP slipped back 0.1 percent, though the country's central bank, the Federal Reserve, indicated the pullback was likely to be brief as it repeated its pledge to continue providing support. European shares, which have surged 3. ...