Add top module comment to all files

src/Distribution/Haddock.hs

src/Haddock/DevHelp.hs

src/Haddock/Exception.hs

src/Haddock/HH.hs

src/Haddock/HH2.hs

src/Haddock/InterfaceFile.hs

src/Haddock/ModuleTree.hs

src/Haddock/Options.hs

src/Haddock/Types.hs

src/Haddock/Utils/GHC.hs

src/Haddock/Version.hs