The Macallan keeps its streak alive as the most coveted Scotch brand on the planet.If you forget about a $20 bill in your coat pocket and find it 30 years laters, it's still worth $20. But the same cannot be said for rare whisky. If you forget about a cask of Scotch you bought for $6,275 in 1988, three decades later, it may be worth nearly $1.3 million. A cask of The Macallan distilled in 1988 is laying claim to the record for most expensive whisky cask ever sold at auction after fetching $1,295,500 on Sunday from an unnamed American...