all: use bytes.Equal, bytes.Contains and strings.Contains

Change-Id: Iba82a5bd3846f7ab038cc10ec72ff6bcd2c0b484
Reviewed-on: https://go-review.googlesource.com/21377
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Dave Cheney <dave@cheney.net>
diff --git a/src/cmd/compile/internal/gc/global_test.go b/src/cmd/compile/internal/gc/global_test.go
index 54d3ed1..f0139e7 100644
--- a/src/cmd/compile/internal/gc/global_test.go
+++ b/src/cmd/compile/internal/gc/global_test.go
@@ -59,7 +59,7 @@
 	if err != nil {
 		log.Fatalf("could not read target: %v", err)
 	}
-	if bytes.Index(out, []byte("scanInt")) != -1 {
+	if bytes.Contains(out, []byte("scanInt")) {
 		log.Fatalf("scanf code not removed from helloworld")
 	}
 }