SF Patch #494863, file.xreadlines() should raise ValueError if file is closed

This makes xreadlines behave like all other file methods
(other than close() which just returns).
diff --git a/Misc/NEWS b/Misc/NEWS
index 8d68533..9ef6912 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -6,6 +6,10 @@
 
 Core and builtins
 
+- file.xreadlines() now raises a ValueError if the file is closed:
+  Previously, an xreadlines object was returned which would raise
+  a ValueError when the xreadlines.next() method was called.
+
 Extension modules
 
 Library