add changelog

debian/changelog

@@ -26,6 +26,7 @@ apt (0.9.7.8) UNRELEASED; urgency=low
       (potentially) used for non deb,dsc content that may contain
       spaces, thanks to Daniel Hartwig and Thomas Bushnell 
       (LP: #1086997)
+  * use sha512 when available (LP: #1098752)
 
  -- Christian Perrier <bubulle@debian.org>  Mon, 24 Dec 2012 07:01:20 +0100