Add a flag to make a client wait for an empty line before exiting in

control mode to avoid stray commands ending up in the shell.

tmux.h

@@ -515,6 +515,7 @@ enum msgtype {
 	MSG_UNLOCK,
 	MSG_WAKEUP,
 	MSG_EXEC,
+	MSG_FLAGS,
 
 	MSG_READ_OPEN = 300,
 	MSG_READ,
@@ -1644,6 +1645,7 @@ struct client {
 #define CLIENT_NOFORK 0x40000000
 #define CLIENT_ACTIVEPANE 0x80000000ULL
 #define CLIENT_CONTROL_PAUSEAFTER 0x100000000ULL
+#define CLIENT_CONTROL_WAITEXIT 0x200000000ULL
 #define CLIENT_ALLREDRAWFLAGS		\
 	(CLIENT_REDRAWWINDOW|		\
 	 CLIENT_REDRAWSTATUS|		\