MINOR: doc: update the manpage and usage message about -S

Add -S in the manpage, and update the usage message.

Should be backported to 1.9.

doc/haproxy.1

@@ -173,6 +173,12 @@ Attempt to connect to the unix socket, and retrieve all the listening sockets
 from the old process. Those sockets will then be used if possible instead of
 binding new ones.
 
+.TP
+\fB\-S <bind>[,<bind options>...]\fP
+In master-worker mode, create a master CLI. This CLI will enable access to the
+CLI of every worker. Useful for debugging, it's a convenient way of accessing a
+leaving process.
+
 .SH LOGGING
 Since HAProxy can run inside a chroot, it cannot reliably access /dev/log.
 For this reason, it uses the UDP protocol to send its logs to the server,

src/haproxy.c

@@ -527,7 +527,7 @@ static void usage(char *name)
 		"        -dV disables SSL verify on servers side\n"
 		"        -sf/-st [pid ]* finishes/terminates old pids.\n"
 		"        -x <unix_socket> get listening sockets from a unix socket\n"
-		"        -S <unix_socket>[,<bind options>...] new stats socket for the master\n"
+		"        -S <bind>[,<bind options>...] new master CLI\n"
 		"\n",
 		name, cfg_maxpconn);
 	exit(1);