TOKYO, Jan 16 - The dollar slumped to three-year lows against the yen on Friday as yen buying against a broadly soft euro spilled over into the dollar/yen market and triggered stop-loss selling in the U.S. unit, traders said. The dollar suddenly fell about a quarter yen to around 105.70 yen , its lowest since September 2000 and down more than half a yen on the day. The Bank of Japan was likely to have intervened at around that level, underpinning the dollar, dealers said.||