Add changelog entry for compression code rework

debian/changelog

@@ -57,6 +57,8 @@ dpkg (1.15.6) UNRELEASED; urgency=low
   * Normalize ar member names when reading (removing trailing spaces and
     slash), this allows deb-split packages be created with GNU ar.
   * Validate compression level on dpkg-deb argument parsing.
+  * Fix error handling, clean up and refactor compression code.
+    Thanks to Jonathan Nieder for several of the patches.
 
   [ Modestas Vainius ]
   * Implement symbol patterns (Closes: #563752). From now on, it is possible to