control_callback replaces ping_callback (API Change):

fix #322

The new callback is informed of all frame types including close.

Actions Required:

* Change calls to websocket::stream::ping_callback to use
  websocket::stream::control_callback

* Change user defined ping callbacks to have the new
  signature and adjust the callback definition appropriately.

doc/quickref.xml

@@ -132,6 +132,7 @@
           <simplelist type="vert" columns="1">
             <member><link linkend="beast.ref.beast__websocket__close_code">close_code</link></member>
             <member><link linkend="beast.ref.beast__websocket__error">error</link></member>
+            <member><link linkend="beast.ref.beast__websocket__frame_type">frame_type</link></member>
           </simplelist>
         </entry>
       </row>