stty(1): list DISCARD control character

bin/stty/stty.1

@@ -401,6 +401,7 @@ Recognized control-characters:
 .It susp Ta Tn VSUSP Ta SUSP No character
 .It start Ta Tn VSTART Ta START No character
 .It stop Ta Tn VSTOP Ta STOP No character
+.It discard Ta Tn VDISCARD Ta DISCARD No character
 .It dsusp Ta Tn VDSUSP Ta DSUSP No character
 .It lnext Ta Tn VLNEXT Ta LNEXT No character
 .It reprint Ta Tn VREPRINT Ta REPRINT No character