Fix small bug
Fix small bug

The rule is to prefer type constructors to other things when an identifier in a
doc string can refer to multiple things. This stopped working with newer GHC
versions (due to a tiny change in the GHC renamer). We implement this rule
in the HTML backend for now, instead of fixing it in GHC, since we will move
renaming of doc strings to Haddock in the future anyway. 

ghcjs/haddock-internal,ghcjs/haddock-internal