patch applied (packages/Cabal): Make unknown fields a warning rather than an error

[Isaac Jones]

Wed Feb  1 10:29:44 PST 2006  Duncan Coutts <duncan.coutts at worc.ox.ac.uk>
  * Make unknown fields a warning rather than an error
  Add support for warnings to the ParseResult type. Change existing
  warnings from using Debug.Trace to use this new warning support.

    M ./Distribution/PackageDescription.hs -4 +6
    M ./Distribution/ParseUtils.hs -13 +22