Add standard boilerplate sentence about when stats_temp_directory can be changed.

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.189 2008/08/25 18:55:43 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.190 2008/08/25 19:03:37 tgl Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -3414,12 +3414,15 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </indexterm>
       <listitem>
        <para>
-        Sets the directory to store temporary statistics data in. This can be a 
-        path relative to the data directory or an absolute path. The default is
-        <filename>pg_stat_tmp</filename>. Pointing this at a RAM based filesystem
-        will decrease physical I/O requirements and can lead to increased 
-        performance. If this parameter is changed when the system is running,
-		there is a small window of time until the new file has been written 
+        Sets the directory to store temporary statistics data in. This can be
+        a path relative to the data directory or an absolute path. The default
+        is <filename>pg_stat_tmp</filename>. Pointing this at a RAM based
+        filesystem will decrease physical I/O requirements and can lead to
+        improved performance.
+        This parameter can only be set in the <filename>postgresql.conf</>
+        file or on the server command line.
+        If this parameter is changed while the server is running, there is a
+        small window of time until the new statistics file has been written
         during which the statistics functions might return no information.
        </para>
       </listitem>