patch applied (packages/Cabal): Validate the docbook xml before processing.

[Ian Lynagh]

Fri Feb 13 05:41:36 PST 2009  Duncan Coutts <duncan at haskell.org>
  * Validate the docbook xml before processing.
  Apparently xsltproc does not validate against the dtd.
  This should stop errors creaping back in.

    M ./Makefile -1 +6

View patch online:
http://darcs.haskell.org/packages/Cabal/_darcs/patches/20090213134136-adfee-90fdd69fa65b3275e8ff8525c98f153c15511d54.gz