Doc/Developing.hs: add some information about Haddock documentation.
Doc/Developing.hs: add some information about Haddock documentation.

darcs-hash:20071219215300-bd4d7-ddf6e83d3e73cbfb22cdf96f0080763a13288199

jthornber/XMonadContrib,jthornber/XMonadContrib