patch applied (ghc): Don't break when asked to install-docs

[Ian Lynagh]

Fri Mar 16 10:00:03 PDT 2007  Ian Lynagh <igloo at earth.li>
  * Don't break when asked to install-docs
  (we don't actually do anything useful either, because Cabal doesn't have
  an install-docs option).

    M ./libraries/Makefile -1 +5