Add haddock versino to release notes

docs/users_guide/7.2.2-notes.xml

@@ -86,11 +86,18 @@
         (<ulink url="http://hackage.haskell.org/trac/ghc/ticket/5436">#5436</ulink>).
       </para>
     </listitem>
+
     <listitem>
       <para>
         The base package is now version 4.4.1.0 (was 4.4.0.0).
       </para>
     </listitem>
+
+    <listitem>
+      <para>
+        Haddock is now version 2.9.4.
+      </para>
+    </listitem>
   </itemizedlist>
 </sect1>