By Tim Hepher and Merissa Marr PARIS (Reuters) - Giant media company Vivendi Universal officially hoisted a for-sale sign over its American entertainment empire on Tuesday, smashing the Hollywood dream of a French firm that slid from boom to near-bust. Almost a year after the ouster of ex-Chief Executive Officer Jean-Marie Messier, who turned Vivendi from a water company into a media titan with huge debts, the veteran company fixer brought in to replace him pulled down the curtain on a three-year dalliance with Tinseltown. Current CEO Jean-Rene Fourtou said Vivendi's future lay in telecommunications and French television -- not...