typo in Foreign.Ptr.minusPtr documentation

[Henning Thielemann]

http://www.haskell.org/ghc/docs/latest/html/libraries/base/Foreign-Ptr.html#v%3AminusPtr

The description "Computes the offset required to get from the first to
the second argument." contradicts to the formula
 p2 == p1 `plusPtr` (p2 `minusPtr` p1)

It should be "Computes the offset required to get from the second to
the first argument."