patch applied (cabal-branches/cabal-1.2): Don't generate links when dependent docs not installed. Fixes bug #157.

[Ian Lynagh]

Mon Sep 24 07:25:20 PDT 2007  Duncan Coutts <duncan at haskell.org>
  * Don't generate links when dependent docs not installed. Fixes bug #157.
  Generates a warning rather than failing as before.

    M ./Distribution/Simple/Haddock.hs -6 +11