Dust off your harem pants for the Hamptons. MC Hammer just signed on to perform at Alexander Soros’ and filmmaker Edward Zwick’s July 7 “Unmasked” gala, one of the big parties to kick off the summer. Anne Hathaway, Emma Thompson, Robert Redford, Arianna Huffington, Evgenia Peretz, Nouriel Roubini, John Sitaras and William Zabel have joined in to support Global Witness. It’s the first gala planned by the Alexander Soros Foundation, which promotes social justice and human rights.