Freddie Mac and Fannie Mae continued their downward spiral on Wednesday in response to a proposal to wind-down the two federally controlled mortgage buyers.Freddie Mac slumped 18% and Fannie Mae fell 17% in the wake of a proposal from U.S. lawmakers to reform housing finance that in effect will liquidate the mortgage buyers. However, the drop in share prices was seen as a surprisegiven the proposal had been largely expected.