Rewrite screen-redraw.c to make it tidier and more maintainable. A scene

is generated and cached in the client: it holds positions and sizes of
panes, borders and so on. The scene is invalidated when a pane is moved
or resized or relevant option is changed. This scene is then drawn to
the client as needed and text and colours are filled in. With Michael
Grant.

cmd-rotate-window.c

@@ -109,6 +109,7 @@ cmd_rotate_window_exec(struct cmd *self, struct cmdq_item *item)
 	window_set_active_pane(w, wp, 1);
 	cmd_find_from_winlink_pane(current, wl, wp, 0);
 	window_pop_zoom(w);
+	redraw_invalidate_scene(w);
 	server_redraw_window(w);
 
 	return (CMD_RETURN_NORMAL);