LONDON, Jan 2(Reuters) - World shares hit their highest level since July 2011 on Wednesday after U.S. markets jumped sharply in response to the deal to prevent a fiscal crunch from sending the giant economy back into recession. MSCI's global share index rose to 346.57 points shortly after Wall Street opened, a peak not seen since July 8, 2011 after which a resurgence in the euro zone debt crisis sparked a sharp sell-off in global equity markets. Wednesday's gains come after the MSCI glo