Document PSTL linker flags

	* doc/xml/manual/using.xml: Add PSTL linker flags to table
        3.1.

From-SVN: r270521

libstdc++-v3/ChangeLog

+2019-04-23  Thomas Rodgers <trodgers@redhat.com>
+
+	Document PSTL linker flags
+
+	* doc/xml/manual/using.xml: Add PSTL linker flags to table
+        3.1.
+	
 2019-04-23  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/std/variant (__detail::__variant::_Traits): Make

libstdc++-v3/doc/xml/manual/using.xml

@@ -107,6 +107,15 @@
       <entry><literal>-fopenmp</literal></entry>
       <entry>For <link linkend="manual.ext.parallel_mode">parallel</link> mode.</entry>
     </row>
+    
+    <row>
+      <entry><literal>-ltbb</literal></entry>
+      <entry>Linking to tbb (Thread Building Blocks) is required for use of the
+        Parallel Standard Algorithms and execution policies in
+        <filename class="headerfile">&lt;execution&gt;</filename>.
+      </entry>
+    </row>
+    
   </tbody>
 
 </tgroup>