Add cross-references from the DECLARE and FETCH reference pages to

the plpgsql documentation about cursors.  Per a suggestion from
Matthew Wakeling.

doc/src/sgml/ref/declare.sgml

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@@ -41,6 +41,15 @@ DECLARE <replaceable class="parameter">name</replaceable> [ BINARY ] [ INSENSITI
    After the cursor is created, rows are fetched from it using
    <xref linkend="sql-fetch" endterm="sql-fetch-title">.
   </para>
+
+  <note>
+   <para>
+    This page describes usage of cursors at the SQL command level.
+    If you are trying to use cursors inside a <application>PL/pgSQL</>
+    function, the rules are different &mdash;
+    see <xref linkend="plpgsql-cursors">.
+   </para>
+  </note>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/fetch.sgml

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@@ -92,6 +92,15 @@ where <replaceable class="PARAMETER">direction</replaceable> can be empty or one
    row.  This will succeed unless the cursor is positioned before the
    first row or after the last row; in which case, no row is returned.
   </para>
+
+  <note>
+   <para>
+    This page describes usage of cursors at the SQL command level.
+    If you are trying to use cursors inside a <application>PL/pgSQL</>
+    function, the rules are different &mdash;
+    see <xref linkend="plpgsql-cursors">.
+   </para>
+  </note>
  </refsect1>
 
  <refsect1>