Function to add to Data.List

[johnw at newartisans.com]

>>>>> Niklas Haas <haskell at nand.wakku.to> writes:

>> Oh yes, 'sortOn' is a really nice name. :)

> Huh, that name just reminded me of GHC.Exts.sortWith:

Either of the names sortOn, or sortWith, sound good.  I think I prefer
sortWith.

John