Restore geometry of all windows before exiting/restarting (Thanks Sasha)

This fixes ticket #185

include/manage.h

@@ -23,6 +23,16 @@
 void manage_existing_windows(xcb_connection_t *conn, xcb_property_handlers_t
                              *prophs, xcb_window_t root);
 
+/**
+ * Restores the geometry of each window by reparenting it to the root window
+ * at the position of its frame.
+ *
+ * This is to be called *only* before exiting/restarting i3 because of evil
+ * side-effects which are to be expected when continuing to run i3.
+ *
+ */
+void restore_geometry(xcb_connection_t *conn);
+
 /**
  * Do some sanity checks and then reparent the window.
  *