further change to support dlist-1.0

Its tail no longer yields a DList.

Utility/TList.hs

@@ -12,6 +12,7 @@
  -}
 
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP #-}
 
 module Utility.TList (
 	TList,
@@ -44,7 +45,11 @@ newTList = newEmptyTMVar
 headTList :: TList a -> STM a
 headTList tlist = do
 	dl <- takeTMVar tlist
+#if MIN_VERSION_dlist(1,0,0)
+	let !dl' = D.fromList $ D.tail dl
+#else
 	let !dl' = D.tail dl
+#endif
 	unless (emptyDList dl') $
 		putTMVar tlist dl'
 	return (D.head dl)