update tree for reflect changes

src/pkg/net/dnsmsg.go

Index: src/pkg/net/dnsmsg.go
===================================================================
--- a/src/pkg/net/dnsmsg.go
+++ b/src/pkg/net/dnsmsg.go
@@ -380,7 +380,7 @@
 // and other (often anonymous) structs.
 func packStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int, ok bool) {
 	for i := 0; i < val.NumField(); i++ {
-		f := val.Type().(*reflect.StructType).Field(i)
+		f := val.Type().Field(i)
 		switch fv := val.Field(i).(type) {
 		default:
 		BadType:
@@ -451,7 +451,7 @@
 // Same restrictions as packStructValue.
 func unpackStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int, ok bool) {
 	for i := 0; i < val.NumField(); i++ {
-		f := val.Type().(*reflect.StructType).Field(i)
+		f := val.Type().Field(i)
 		switch fv := val.Field(i).(type) {
 		default:
 		BadType:
@@ -523,7 +523,7 @@
 		if i > 0 {
 			s += ", "
 		}
-		f := val.Type().(*reflect.StructType).Field(i)
+		f := val.Type().Field(i)
 		if !f.Anonymous {
 			s += f.Name + "="
 		}