release notes: add two optimizer items

Report by Tom Lane

Author: bmomjian

doc/src/sgml/release-9.5.sgml

@@ -240,6 +240,21 @@
        </para>
       </listitem>
 
+      <listitem>
+       <para>
+        Allow the optimizer to remove unnecessary references to left
+        outer join subqueries (David Rowley)
+       </para>
+      </listitem>
+
+      <listitem>
+       <para>
+        Allow pushdown of query restrictions into <link
+        linkend="functions-window">window functions</>, where appropriate
+        (David Rowley)
+       </para>
+      </listitem>
+
       <listitem>
        <para>
         Speed up <acronym>CRC</> (cyclic redundancy check) computations