Federal election filings released Wednesday show that more than 60 corporations and wealthy individuals gave checks of more than $100,000 to Mitt Romney’s super PAC, Restore Our Future, which took in about $18 million in the second half of 2011. The haul underwrote Romney’s multimillion-dollar advertising blitz that has buried his rivals in early primary states. Most of the donors are from the finance industry, including Goldman Sachs executives and hedge-fund managers. Texas construction magnate Harlan Crowe gave $300,000, and the Koch brothers gave $1 million. Without giving through the super PAC, each of the donors would legally be allowed to contribute only $2,500 to the campaign.