Bugfix: Also fix horizontal resizing

The same problem as in the commit before this one was present. Additionally,
the dock_clients and internal bar were not taken into account everywhere.

include/workspace.h

@@ -83,4 +83,17 @@ void workspace_map_clients(xcb_connection_t *conn, Workspace *ws);
  */
 void workspace_update_urgent_flag(Workspace *ws);
 
+/*
+ * Returns the width of the workspace.
+ *
+ */
+int workspace_width(Workspace *ws);
+
+/*
+ * Returns the effective height of the workspace (without the internal bar and
+ * without dock clients).
+ *
+ */
+int workspace_height(Workspace *ws);
+
 #endif