Update rigctl.1 to include W command

doc/man1/rigctl.1

@@ -1071,6 +1071,25 @@ option above, will terminate each command string sent to the radio.  This
 character should not be a part of the input string.
 .
 .TP
+.BR W ", " send_cmd_rx " \(aq" \fICmd\fP \(aq
+Send a raw command string to the radio and expect a number of bytes returned.
+.IP
+This is useful for testing and troubleshooting radio commands and responses when
+developing a backend.  If the # of bytes requested is <= the number actually returnead no timeout will occur.
+.IP
+The command argument can have no spaces in it.
+For binary protocols enter values as \\0xAA\\0xBB.  Expect a
+.RI \(aq Reply \(aq
+from the radio which will likely be a binary block or an ASCII string
+depending on the radio's protocol (see your radio's computer control
+documentation).
+.IP
+The command terminator, set by the
+.B send-cmd-term
+option above, will terminate each command string sent to the radio.  This
+character should not be a part of the input string.
+.
+.TP
 .BR pause " \(aq" \fISeconds\fP \(aq
 Pause for the given whole (integer) number of
 .RI \(aq Seconds \(aq