Don't expose the unfolding of dictionary selectors without -O
When compiling without -O we were getting code like this f x = case GHC.Base.$f20 of :DEq eq neq -> eq x x But because of the -O the $f20 dictionary is not available, so exposing the dictionary selector was useless. Yet it makes the code bigger! Better to get f x = GHC.Base.== GHC.Bsae.$f20 x x This patch suppresses the implicit unfolding for dictionary selectors when compiling without -O. We could do the same for other implicit Ids, but this will do for now. There should be no effect when compiling with -O. Programs should be smaller without -O and may run a tiny bit slower.