docs: mention CREATE TABLE LIKE linkage using INCLUDING DEFAULTS

Mention that CREATE TABLE LIKE INCLUDING DEFAULTS creates a link between
the original and new tables if a default function modifies the database,
like nextval().

doc/src/sgml/ref/create_table.sgml

@@ -329,7 +329,10 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
      </para>
      <para>
       Default expressions for the copied column definitions will only be
-      copied if <literal>INCLUDING DEFAULTS</literal> is specified.  The
+      copied if <literal>INCLUDING DEFAULTS</literal> is specified. 
+      Defaults that call database-modification functions, like
+      <function>nextval</>, create a linkage between the original and
+      new tables.  The
       default behavior is to exclude default expressions, resulting in the
       copied columns in the new table having null defaults.
      </para>