title: Enable --hyperlink-source for "cabal install"
body: <p>The command <code>cabal haddock</code> has very useful --hyperlink-source option.
  I would like to have the source hyperlinked when building documentation with <code>cabal install</code>.</p>
  
  <p>The ticket #517 seems to be just about it: <a href="http://hackage.haskell.org/trac/hackage/ticket/517" rel="noreferrer">http://hackage.haskell.org/trac/hackage/ticket/517</a></p>
  
  <p>However, perhaps it is possible to set this flag via ~/.cabal/config file?</p>
  
  <p>If not, how can I get working cabal-install build with the patch from #517 without installing Cabal-1.9, which is currently mandatory (due to one patch from December)?</p>