Gold and silver suffered their biggest slide in years, in a whipsawing reversal of a scorching rally that lifted prices to all-time highs.Gold dropped as much as 8% to crash through $5,000 an ounce, while silver plunged more than 20% in the biggest intraday drop since 2008 as the selloff swept through the broader metals markets. Copper fell almost 4% in London, after surging above $14,000 a ton for the first time Thursday in its biggest intraday jump since 2008.A wave of investor demand into precious metals ...