Replace SYB traversals

haddock-api/haddock-api.cabal

haddock-api/src/Haddock/Backends/Xhtml/Decl.hs

haddock-api/src/Haddock/Backends/Xhtml/Layout.hs

haddock-api/src/Haddock/Convert.hs

haddock-api/src/Haddock/Interface.hs

haddock-api/src/Haddock/Interface/AttachInstances.hs

haddock-api/src/Haddock/Interface/Rename.hs

haddock-api/src/Haddock/Interface/RenameType.hs

haddock-api/src/Haddock/Syb.hs

haddock-api/src/Haddock/Types.hs

haddock.cabal

html-test/ref/Bug1004.html

html-test/ref/Bug1033.html

html-test/ref/Bug1054.html

html-test/ref/Bug466.html

html-test/ref/Bug548.html

html-test/ref/Bug923.html

html-test/ref/BugDeprecated.html

html-test/ref/BugExportHeadings.html

html-test/ref/DeprecatedClass.html