docs: mention windows quoting change in 9.4 release notes

Report by Heikki Linnakangas

doc/src/sgml/release-9.4.sgml

@@ -201,6 +201,21 @@
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      On Windows, automatically preserve quotes in command strings supplied
+      by the user (Heikki Linnakangas)
+     </para>
+
+     <para>
+      User commands that did their own quote preservation might need
+      adjustment, e.g.  <link
+      linkend="guc-archive-command">archive_command</link>, <link
+      linkend="restore-command">restore_command</link>, <command>COPY TO/FROM
+      PROGRAM</>.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       Remove system column <link