docs: cleanup/remove/update references to OID column.

I (Andres) missed these in 578b229718.

Author: Justin Pryzby, editorialized a bit by Andres Freund
Reviewed-By: Daniel Verite, Andres Freund
Discussion: https://postgr.es/m/20190408002847.GA904@telsasoft.com

doc/src/sgml/catalogs.sgml

@@ -1047,7 +1047,7 @@
       <entry></entry>
       <entry>
        The number of the column.  Ordinary columns are numbered from 1
-       up.  System columns, such as <structfield>oid</structfield>,
+       up.  System columns, such as <structfield>ctid</structfield>,
        have (arbitrary) negative numbers.
       </entry>
      </row>

doc/src/sgml/ddl.sgml

@@ -1202,8 +1202,7 @@ CREATE TABLE circles (
       <structfield>ctid</structfield> will change if it is
       updated or moved by <command>VACUUM FULL</command>.  Therefore
       <structfield>ctid</structfield> is useless as a long-term row
-      identifier.  The OID, or even better a user-defined serial
-      number, should be used to identify logical rows.
+      identifier.  A primary key should be used to identify logical rows.
      </para>
     </listitem>
    </varlistentry>
@@ -3675,8 +3674,7 @@ VALUES ('Albany', NULL, NULL, 'NY');
        <command>CREATE TABLE</command>, nor is it possible to add columns to
        partitions after-the-fact using <command>ALTER TABLE</command>.  Tables may be
        added as a partition with <command>ALTER TABLE ... ATTACH PARTITION</command>
-       only if their columns exactly match the parent, including any
-       <literal>oid</literal> column.
+       only if their columns exactly match the parent.
       </para>
      </listitem>
 

doc/src/sgml/information_schema.sgml

@@ -1312,7 +1312,7 @@
   <para>
    The view <literal>columns</literal> contains information about all
    table columns (or view columns) in the database.  System columns
-   (<literal>oid</literal>, etc.) are not included.  Only those columns are
+   (<literal>ctid</literal>, etc.) are not included.  Only those columns are
    shown that the current user has access to (by way of being the
    owner or having some privilege).
   </para>

doc/src/sgml/ref/create_trigger.sgml

@@ -465,7 +465,7 @@ UPDATE OF <replaceable>column_name1</replaceable> [, <replaceable>column_name2</
    that the <literal>NEW</literal> row seen by the condition is the current value,
    as possibly modified by earlier triggers.  Also, a <literal>BEFORE</literal>
    trigger's <literal>WHEN</literal> condition is not allowed to examine the
-   system columns of the <literal>NEW</literal> row (such as <literal>oid</literal>),
+   system columns of the <literal>NEW</literal> row (such as <literal>ctid</literal>),
    because those won't have been set yet.
   </para>
 

doc/src/sgml/ref/insert.sgml

@@ -551,14 +551,12 @@ INSERT INTO <replaceable class="parameter">table_name</replaceable> [ AS <replac
 <screen>
 INSERT <replaceable>oid</replaceable> <replaceable class="parameter">count</replaceable>
 </screen>
-   The <replaceable class="parameter">count</replaceable> is the
-   number of rows inserted or updated.  If <replaceable
-   class="parameter">count</replaceable> is exactly one, and the
-   target table has OIDs, then <replaceable
-   class="parameter">oid</replaceable> is the <acronym>OID</acronym>
-   assigned to the inserted row.  The single row must have been
-   inserted rather than updated.  Otherwise <replaceable
-   class="parameter">oid</replaceable> is zero.
+   The <replaceable class="parameter">count</replaceable> is the number of
+   rows inserted or updated.  <replaceable>oid</replaceable> is always 0 (it
+   used to be the <acronym>OID</acronym> assigned to the inserted row if
+   <replaceable>rows</replaceable> was exactly one and the target table was
+   declared <literal>WITH OIDS</literal> and 0 otherwise, but creating a table
+   <literal>WITH OIDS</literal> is not supported anymore).
   </para>
 
   <para>

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

@@ -3794,6 +3794,9 @@ bar
         command. This variable is only guaranteed to be valid until
         after the result of the next <acronym>SQL</acronym> command has
         been displayed.
+        <productname>PostgreSQL</productname> servers since version 12 do not
+        support OID system columns anymore, thus LASTOID will always be 0
+        following <command>INSERT</command> when targeting such servers.
         </para>
         </listitem>
       </varlistentry>

doc/src/sgml/spi.sgml

@@ -3105,7 +3105,7 @@ int SPI_fnumber(TupleDesc <parameter>rowdesc</parameter>, const char * <paramete
 
   <para>
    If <parameter>colname</parameter> refers to a system column (e.g.,
-   <literal>oid</literal>) then the appropriate negative column number will
+   <literal>ctid</literal>) then the appropriate negative column number will
    be returned.  The caller should be careful to test the return value
    for exact equality to <symbol>SPI_ERROR_NOATTRIBUTE</symbol> to
    detect an error; testing the result for less than or equal to 0 is