testing: style change: omit unnecessary new

This was brought to my attention because a user thought that because
the file was named "example.go" it served as an example of good coding
practice.  It's not an example, of course, but may as well use a more
idiomatic style anyhow.

Change-Id: I7aa720f603f09f7d597fb7536dbf46ef09144e28
Reviewed-on: https://go-review.googlesource.com/1902Reviewed-by: Minux Ma <minux@golang.org>

src/testing/example.go

@@ -56,8 +56,8 @@ func runExample(eg InternalExample) (ok bool) {
 	os.Stdout = w
 	outC := make(chan string)
 	go func() {
-		buf := new(bytes.Buffer)
-		_, err := io.Copy(buf, r)
+		var buf bytes.Buffer
+		_, err := io.Copy(&buf, r)
 		r.Close()
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "testing: copying pipe: %v\n", err)