Clarify documentation around pg_dump -t option

The behavior is different for different types of objects, so make that
more clear.

Author: Ian Barwick

doc/src/sgml/ref/pg_dump.sgml

@@ -517,9 +517,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Dump only tables with names matching
-        <replaceable class="parameter">pattern</replaceable>.
-        For this purpose, <quote>table</quote> includes views, materialized views,
-        sequences, and foreign tables.  Multiple tables
+        <replaceable class="parameter">pattern</replaceable>. Multiple tables
         can be selected by writing multiple <option>-t</option> switches.  The
         <replaceable class="parameter">pattern</replaceable> parameter is
         interpreted as a pattern according to the same rules used by
@@ -531,6 +529,14 @@ PostgreSQL documentation
         <xref linkend="pg-dump-examples"/> below.
        </para>
 
+       <para>
+        As well as tables, this option can be used to dump views, materialized views,
+        foreign tables, and sequence definitions.  However it will not dump the contents
+        of views or materialized views, and the contents of foreign tables will only be
+        dumped if the corresponding foreign server is specified with
+        <option>--include-foreign-data</option>.
+       </para>
+
        <para>
         The <option>-n</option> and <option>-N</option> switches have no effect when
         <option>-t</option> is used, because tables selected by <option>-t</option> will