Add a client flag 'active-pane' which stores the active pane in the

client and allows it to be changed independently from the real active
pane stored in the window. This is can be used with session groups which
allow an independent current window (although it would be nice to have a
flag for this too and remove session groups). The client active pane is
only really useful interactively, many things (hooks, window-style,
zooming) still use the window active pane.

cmd-break-pane.c

@@ -89,6 +89,7 @@ cmd_break_pane_exec(struct cmd *self, struct cmdq_item *item)
 	}
 
 	TAILQ_REMOVE(&w->panes, wp, entry);
+	server_client_remove_pane(wp);
 	window_lost_pane(w, wp);
 	layout_close_pane(wp);