Update Changelog, put back large message from field for extra headers

test case.  Keep simplified message also in case further debugging is needed.

ChangeLog

@@ -1,6 +1,6 @@
 UNRELEASED Version 0.5
-    - Add test case for <https://launchpad.net/bugs/644046>
-    - Add test case for <https://launchpad.net/bugs/737311>
+    - Add test case and fix for <https://launchpad.net/bugs/644046>
+    - Add test case and fix for <https://launchpad.net/bugs/737311>
     - Fix dkim.fold()
 
 2011-06-16 Version 0.4.2