sysupdate/psfax/play: fix unquoted brackets causing rc to perform unnecessary file lookups

rc/bin/play

@@ -76,7 +76,7 @@ fn play1 {
 }
 
 fn usage {
-	echo usage: $argv0 [ -o file ] [ file ... ] >[1=2]
+	echo usage: $argv0 '[ -o file ] [ file ... ]' >[1=2]
 	exit usage
 }
 

rc/bin/psfax

@@ -10,7 +10,7 @@ case -v
 
 switch($#*){
 case 0 1
-	echo usage: $0 telephone-number recipient [files]
+	echo usage: $0 telephone-number recipient '[files]'
 	exit 0
 case 2
 	stdin=yes

rc/bin/sysupdate

@@ -8,7 +8,7 @@ while(! ~ $#* 0){
 	case -i
 		hg incoming
 	case *
-		echo usage: sysupdate [-i] >[1=2]
+		echo usage: sysupdate '[-i]' >[1=2]
 		exit usage
 	}
 	shift