fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Utility/TList.hs

@@ -57,7 +57,7 @@ modifyTList tlist a = do
 	unless (emptyDList dl') $
 		putTMVar tlist dl'
   where
-  	emptyDList = D.list True (\_ _ -> False)
+	emptyDList = D.list True (\_ _ -> False)
 
 consTList :: TList a -> a -> STM ()
 consTList tlist v = modifyTList tlist $ \dl -> D.cons v dl