Enable TypeOperators to use (~)

GHC Proposal #371 requires TypeOperators to use type equality a~b.
The following lines are affected:

	containers/src/Data/Sequence/Internal.hs
	4416:instance a ~ Char => IsString (Seq a) where

The fix is to simply enable the extension.

Author: int-index

containers/src/Data/Sequence/Internal.hs

@@ -15,6 +15,7 @@
 {-# LANGUAGE ViewPatterns #-}
 #endif
 {-# LANGUAGE PatternGuards #-}
+{-# LANGUAGE TypeOperators #-}
 
 {-# OPTIONS_HADDOCK not-home #-}
 {-# OPTIONS_GHC -fno-warn-incomplete-uni-patterns #-}