Xhtml.Decl: Show kind signatures for type family variables
Xhtml.Decl: Show kind signatures for type family variables

Addresses GHC #11588.

niteria/haddock,Helkafen/haddock,idontgetoutmuch/haddock,Fuuzetsu/haddock,haskell/haddock,haskell/haddock,niteria/haddock,Fuuzetsu/haddock,haskell/haddock,Fuuzetsu/haddock,haskell/haddock,idontgetoutmuch/haddock,Helkafen/haddock,idontgetoutmuch/haddock,niteria/haddock,haskell/haddock,Helkafen/haddock,Fuuzetsu/haddock