Add links to documentation sections in 9.0 release notes.

Also update tagging instructions, and add id tags to a few documentation
sections.

doc/src/sgml/ref/psql-ref.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.242 2010/03/08 12:38:37 mha Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.243 2010/03/21 00:43:40 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -627,7 +627,7 @@ testdb=&gt;
     </para>
   </refsect2>
 
-  <refsect2>
+  <refsect2 id="APP-PSQL-meta-commands">
     <title>Meta-Commands</title>
 
     <para>

doc/src/sgml/release.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.636 2010/03/20 03:12:52 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.637 2010/03/21 00:43:40 momjian Exp $ -->
 <!--
 
 Typical markup:
@@ -6,12 +6,13 @@ Typical markup:
 &<>                             use & escapes
 PostgreSQL                      <productname>
 postgresql.conf, pg_hba.conf    <filename>
-[A-Z][A-Z ]+[A-Z]               <command>, <literal>
+[A-Z][A-Z ]+[A-Z]               <command>, <literal>, <envar>
 [A-Za-z_][A-Za-z0-9_]+()        <function>
 -[-A-Za-z_]+                    <option>
 [A-Za-z_]/[A-Za-z_]+            <filename>
+psql                            <application>
 pg_[A-Za-z0-9_]+                <application>, <structname>
-[A-Z][A-Z][A-Z_ ]*              <type>, <varname>, <envar>, <literal>
+[A-Z][A-Z][A-Z_ ]*              <type>, <varname>
 
 non-ASCII characters            convert to HTML4 entity (&) escapes
 

doc/src/sgml/runtime.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.432 2010/03/13 11:00:19 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.433 2010/03/21 00:43:40 momjian Exp $ -->
 
 <chapter Id="runtime">
  <title>Server Setup and Operation</title>
@@ -1221,7 +1221,7 @@ default:\
    </para>
   </sect2>
 
-  <sect2>
+  <sect2 id="linux-memory-overcommit">
    <title>Linux Memory Overcommit</title>
 
    <para>