Put documentation on XML data type and functions in better positions. Add

some index terms.

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.118 2007/03/26 01:41:57 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.119 2007/04/02 15:27:02 petere Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -3591,7 +3591,7 @@ SELECT * FROM parent WHERE key = 2400;
        <primary><varname>SET XML OPTION</></primary>
       </indexterm>
       <indexterm>
-       <primary><varname>XML option</></primary>
+       <primary>XML option</primary>
       </indexterm>
       <listitem>
        <para>