add missing bugnumber

debian/changelog

@@ -2,7 +2,7 @@ apt (0.7.17~exp3) experimental; urgency=low
 
   * apt-pkg/acquire-item.cc:
     - fix a merge mistake that prevents the fallback to the 
-      uncompressed 'Packages' to work correctly
+      uncompressed 'Packages' to work correctly (closes: #409284)
 
  -- Michael Vogt <mvo@debian.org>  Wed, 29 Oct 2008 09:36:24 +0100