The usage string: renice [priority | [-n incr]] ... assumed that the part

`priority | [-n incr]' was optionnal which is wrong according to the code.
Add FreeBSD Id.
Reviewed by:	maxim

usr.bin/renice/renice.8

@@ -40,7 +40,12 @@
 .Nd alter priority of running processes
 .Sh SYNOPSIS
 .Nm
-.Op Ar priority | Op Fl n Ar increment
+.Ar priority
+.Op Oo Fl p Oc Ar pid ...
+.Op Oo Fl g Oc Ar pgrp ...
+.Op Oo Fl u Oc Ar user ...
+.Nm
+.Fl n Ar increment
 .Op Oo Fl p Oc Ar pid ...
 .Op Oo Fl g Oc Ar pgrp ...
 .Op Oo Fl u Oc Ar user ...

usr.bin/renice/renice.c

@@ -37,13 +37,14 @@ static const char copyright[] =
 	The Regents of the University of California.  All rights reserved.\n";
 #endif /* not lint */
 
-#ifndef lint
 #if 0
+#ifndef lint
 static char sccsid[] = "@(#)renice.c	8.1 (Berkeley) 6/9/93";
-#endif
-static const char rcsid[] =
-  "$FreeBSD$";
 #endif /* not lint */
+#endif
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
 
 #include <sys/types.h>
 #include <sys/time.h>
@@ -179,7 +180,7 @@ static void
 usage()
 {
 	fprintf(stderr, "%s\n%s\n",
-"usage: renice [priority | [-n incr]] [[-p] pid ...] [[-g] pgrp ...]",
-"              [[-u] user ...]");
+"usage: renice priority     [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]",
+"       renice -n increment [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]");
 	exit(1);
 }