links to functions-window

There is a curious oversight in the windows documentation, where
the several window pages are not linking to the functions-window
(where the actual functions are enumerated).

That makes it easy to overlook for instance, a function like row_number() (not mentioned in other
examples).

I think at least the below three links should be added.

Erik Rijkers

--- advanced.sgml.orig 2010-07-01 19:02:56.000000000 +0200
+++ advanced.sgml 2010-07-01 19:05:07.000000000 +0200
@@ -554,6 +554,7 @@
<para>
More details about window functions can be found in
<xref linkend="syntax-window-functions">,
+ <xref linkend="functions-window">,
<xref linkend="queries-window">, and the
<xref linkend="sql-select"> reference page.
</para>

--- syntax.sgml.orig 2010-07-01 19:06:08.000000000 +0200
+++ syntax.sgml 2010-07-01 19:06:42.000000000 +0200
@@ -1761,7 +1761,8 @@

<para>
More information about window functions can be found in
- <xref linkend="tutorial-window"> and
+ <xref linkend="tutorial-window">,
+ <xref linkend="functions-window">,
<xref linkend="queries-window">.
</para>
</sect2>

--- queries.sgml.orig 2010-07-01 19:46:32.000000000 +0200
+++ queries.sgml 2010-07-01 19:47:16.000000000 +0200
@@ -979,7 +979,8 @@

<para>
If the query contains any window functions (see
- <xref linkend="tutorial-window"> and
+ <xref linkend="tutorial-window">,
+ <xref linkend="functions-window"> and
<xref linkend="syntax-window-functions">), these functions are evaluated
after any grouping, aggregation, and <literal>HAVING</> filtering is
performed. That is, if the query uses any aggregates, <literal>GROUP