Disable NFData instances for GHC types when GHC >= 8.0.2

(cherry picked from commit a3309e7)
(cherry picked from commit d9bb5fc)

Author: Simon Marlow

haddock-api/src/Haddock/Types.hs

@@ -1,4 +1,6 @@
-{-# LANGUAGE DeriveDataTypeable, DeriveFunctor, DeriveFoldable, DeriveTraversable, StandaloneDeriving, TypeFamilies, RecordWildCards #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveDataTypeable, DeriveFunctor, DeriveFoldable, DeriveTraversable, StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies, RecordWildCards #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 -----------------------------------------------------------------------------
 -- |
@@ -447,10 +449,12 @@ instance (NFData a, NFData mod)
     DocExamples a             -> a `deepseq` ()
     DocHeader a               -> a `deepseq` ()
 
-
+#if !MIN_VERSION_ghc(8,0,2)
+-- These were added to GHC itself in 8.0.2
 instance NFData Name where rnf x = seq x ()
 instance NFData OccName where rnf x = seq x ()
 instance NFData ModuleName where rnf x = seq x ()
+#endif
 
 instance NFData id => NFData (Header id) where
   rnf (Header a b) = a `deepseq` b `deepseq` ()