TOPWRAP 6-Central banks call turn in economy as optimism stirs

* Global economy about to turn corner: central bankers

* China c.banker hails stimulus effect; crude imports jump

* Surveys show confidence rising in some major economies

* U.S. budget deficit forecast raised by White House

* Stocks fall in U.S., Europe

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By John Wallace

NEW YORK, May 11 (Reuters) - The global economy is about to turn the corner, leading central bankers said on Monday, but there were signs recovery could be long and painful for many around the world.