FIX #1270: add Eq instances for STUArray and IOUArray

Data/Array/Base.hs

@@ -1115,6 +1115,10 @@ data STUArray s i a = STUArray !i !i !Int !(MutableByteArray s)
 
 INSTANCE_TYPEABLE3(STUArray,stUArrayTc,"STUArray")
 
+instance Eq (STUArray s i e) where
+    STUArray _ _ _ arr1# == STUArray _ _ _ arr2# =
+        sameMutableByteArray# arr1# arr2#
+
 #ifdef __GLASGOW_HASKELL__
 {-# INLINE unsafeNewArraySTUArray_ #-}
 unsafeNewArraySTUArray_ :: Ix i

Data/Array/IO/Internals.hs

@@ -77,6 +77,9 @@ newtype IOUArray i e = IOUArray (STUArray RealWorld i e)
 
 INSTANCE_TYPEABLE2(IOUArray,iOUArrayTc,"IOUArray")
 
+instance Eq (IOUArray i e) where
+    IOUArray s1 == IOUArray s2  =  s1 == s2
+
 instance MArray IOUArray Bool IO where
     {-# INLINE getBounds #-}
     getBounds (IOUArray arr) = stToIO $ getBounds arr