For GHC, implement the Typeable.hs macros using standalone deriving

As well as being more pleasant, this fixes #1841:
    Data.Typeable: Instances of basic types don't provide qualified
    strings to mkTyCon

array.cabal

@@ -40,6 +40,8 @@ library
       TypeSynonymInstances
   if impl(ghc)
     extensions:
+      DeriveDataTypeable,
+      StandaloneDeriving,
       Rank2Types,
       MagicHash,
       UnboxedTuples,

include/Typeable.h

@@ -14,32 +14,22 @@
 #ifndef TYPEABLE_H
 #define TYPEABLE_H
 
-#define INSTANCE_TYPEABLE0(tycon,tcname,str) \
-tcname :: TyCon; \
-tcname = mkTyCon str; \
-instance Typeable tycon where { typeOf _ = mkTyConApp tcname [] }
-
 #ifdef __GLASGOW_HASKELL__
 
---  // For GHC, the extra instances follow from general instance declarations
---  // defined in Data.Typeable.
+--  // For GHC, we can use DeriveDataTypeable + StandaloneDeriving to
+--  // generate the instances.
 
-#define INSTANCE_TYPEABLE1(tycon,tcname,str) \
-tcname :: TyCon; \
-tcname = mkTyCon str; \
-instance Typeable1 tycon where { typeOf1 _ = mkTyConApp tcname [] }
+#define INSTANCE_TYPEABLE0(tycon,tcname,str) deriving instance Typeable tycon
+#define INSTANCE_TYPEABLE1(tycon,tcname,str) deriving instance Typeable1 tycon
+#define INSTANCE_TYPEABLE2(tycon,tcname,str) deriving instance Typeable2 tycon
+#define INSTANCE_TYPEABLE3(tycon,tcname,str) deriving instance Typeable3 tycon
 
-#define INSTANCE_TYPEABLE2(tycon,tcname,str) \
-tcname :: TyCon; \
-tcname = mkTyCon str; \
-instance Typeable2 tycon where { typeOf2 _ = mkTyConApp tcname [] }
+#else /* !__GLASGOW_HASKELL__ */
 
-#define INSTANCE_TYPEABLE3(tycon,tcname,str) \
+#define INSTANCE_TYPEABLE0(tycon,tcname,str) \
 tcname :: TyCon; \
 tcname = mkTyCon str; \
-instance Typeable3 tycon where { typeOf3 _ = mkTyConApp tcname [] }
-
-#else /* !__GLASGOW_HASKELL__ */
+instance Typeable tycon where { typeOf _ = mkTyConApp tcname [] }
 
 #define INSTANCE_TYPEABLE1(tycon,tcname,str) \
 tcname = mkTyCon str; \