log: fix example (fix build)

R=golang-dev
CC=golang-dev
https://golang.org/cl/43780043

src/pkg/log/example_test.go

@@ -17,5 +17,5 @@ func ExampleLogger() {
 
 	fmt.Print(&buf)
 	// Output:
-	// logger: example_test.go:15: Hello, log file!
+	// logger: example_test.go:16: Hello, log file!
 }