tutorial fixes

R=r
CC=go-dev
http://go/go-review/1024014

doc/progs/cat_rot13.go

@@ -11,7 +11,7 @@ import (
 	"os";
 )
 
-var rot13_flag = flag.Bool("rot13", false, "rot13 the input")
+var rot13Flag = flag.Bool("rot13", false, "rot13 the input")
 
 func rot13(b byte) byte {
 	if 'a' <= b && b <= 'z' {
@@ -53,7 +53,7 @@ func cat(r reader) {
 	const NBUF = 512;
 	var buf [NBUF]byte;
 
-	if *rot13_flag {
+	if *rot13Flag {
 		r = newRotate13(r)
 	}
 	for {

doc/progs/echo.go

@@ -9,7 +9,7 @@ import (
 	"flag";  // command line option parser
 )
 
-var n_flag = flag.Bool("n", false, "don't print final newline")
+var omitNewline = flag.Bool("n", false, "don't print final newline")
 
 const (
 	Space = " ";
@@ -25,7 +25,7 @@ func main() {
 		}
 		s += flag.Arg(i)
 	}
-	if !*n_flag {
+	if !*omitNewline {
 		s += Newline
 	}
 	os.Stdout.WriteString(s);