minor doc improvement

This patch adds a few additional <xref> tags to the docs, where they
seemed appropriate. I applied this patch to HEAD.

(Suggetions for additional cross refs that would be useful are
welcome; I just added the first few I noticed.)

-Neil
Index: doc/src/sgml/runtime.sgml
===================================================================
RCS file: /var/lib/cvs/pgsql-server/doc/src/sgml/runtime.sgml,v
retrieving revision 1.242
diff -c -r1.242 runtime.sgml
*** a/doc/src/sgml/runtime.sgml    23 Feb 2004 20:45:58 -0000    1.242
--- b/doc/src/sgml/runtime.sgml    1 Mar 2004 17:52:51 -0000
***************
*** 1562,1572 ****
        <term><varname>default_statistics_target</varname> (<type>integer</type>)</term>
        <listitem>
         <para>
!         Sets the default statistics target for table columns that have not
!         had a column-specific target set via <command>ALTER TABLE SET
!         STATISTICS</>.  Larger values increase the time needed to do
!         <command>ANALYZE</>, but may improve the quality of the planner's
!         estimates. The default is 10.
         </para>
        </listitem>
       </varlistentry>
--- 1562,1574 ----
        <term><varname>default_statistics_target</varname> (<type>integer</type>)</term>
        <listitem>
         <para>
!         Sets the default statistics target for table columns that have
!         not had a column-specific target set via <command>ALTER TABLE
!         SET STATISTICS</>.  Larger values increase the time needed to
!         do <command>ANALYZE</>, but may improve the quality of the
!         planner's estimates. The default is 10. For more information
!         on the use of statistics by the <productname>PostgreSQL</>
!         query planner, refer to <xref linkend="planner-stats">.
         </para>
        </listitem>
       </varlistentry>
Index: doc/src/sgml/ref/alter_table.sgml
===================================================================
RCS file: /var/lib/cvs/pgsql-server/doc/src/sgml/ref/alter_table.sgml,v
retrieving revision 1.64
diff -c -r1.64 alter_table.sgml
*** a/doc/src/sgml/ref/alter_table.sgml    1 Dec 2003 22:07:58 -0000    1.64
--- b/doc/src/sgml/ref/alter_table.sgml    1 Mar 2004 17:35:11 -0000
***************
*** 114,120 ****
        sets the per-column statistics-gathering target for subsequent
        <xref linkend="sql-analyze" endterm="sql-analyze-title"> operations.
        The target can be set in the range 0 to 1000; alternatively, set it
!       to -1 to revert to using the system default statistics target.
       </para>
      </listitem>
     </varlistentry>
--- 114,123 ----
        sets the per-column statistics-gathering target for subsequent
        <xref linkend="sql-analyze" endterm="sql-analyze-title"> operations.
        The target can be set in the range 0 to 1000; alternatively, set it
!       to -1 to revert to using the system default statistics
!       target. For more information on the use of statistics by the
!       <productname>PostgreSQL</productname> query planner, refer to
!       <xref linkend="planner-stats">.
       </para>
      </listitem>
     </varlistentry>
Index: doc/src/sgml/ref/create_table.sgml
===================================================================
RCS file: /var/lib/cvs/pgsql-server/doc/src/sgml/ref/create_table.sgml,v
retrieving revision 1.77
diff -c -r1.77 create_table.sgml
*** a/doc/src/sgml/ref/create_table.sgml    1 Dec 2003 22:07:58 -0000    1.77
--- b/doc/src/sgml/ref/create_table.sgml    1 Mar 2004 17:30:16 -0000
***************
*** 151,157 ****
      <term><replaceable class="PARAMETER">data_type</replaceable></term>
      <listitem>
       <para>
!       The data type of the column. This may include array specifiers.
       </para>
      </listitem>
     </varlistentry>
--- 151,160 ----
      <term><replaceable class="PARAMETER">data_type</replaceable></term>
      <listitem>
       <para>
!       The data type of the column. This may include array
!       specifiers. For more information on the data types included with
!       <productname>PostgreSQL</productname>, refer to <xref
!       linkend="datatype">.
       </para>
      </listitem>
     </varlistentry>