ewmh: implement support for _NET_WORKAREA (rdesktop can use that)

Please note that rdesktop’s -g workarea option will not work on
64-bit systems at the moment because of a bug in rdesktop (see the
rdesktop-devel mailing list).

include/ewmh.h

@@ -29,4 +29,14 @@ void ewmh_update_current_desktop();
  */
 void ewmh_update_active_window(xcb_window_t window);
 
+/**
+ * Updates the workarea for each desktop.
+ *
+ * EWMH: Contains a geometry for each desktop. These geometries specify an area
+ * that is completely contained within the viewport. Work area SHOULD be used by
+ * desktop applications to place desktop icons appropriately.
+ *
+ */
+void ewmh_update_workarea();
+
 #endif