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

Mon Sep 24 07:25:20 PDT 2007 Duncan Coutts <duncan@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