Sen. Ted Kennedy's brother-in-law is the mystery witness who raised $100,000 for Sen. Hillary Rodham Clinton and then went undercover and wore a wire to help the feds nab one of her top moneymen on charges of fund-raising-fraud, The Post has learned. The witness, Ray Reggie, 43, has a sister, Victoria, who married Kennedy in 1992, and prosecutors say Reggie secretly recorded "incriminating" statements made by David Rosen, a top Clinton fund-raiser. Reggie was close enough to Bill and Hillary Clinton to sleep over at the White House in 2000 and stay up chatting with the first couple into the...