update vendoring (#72)

vendor/github.com/golang/protobuf/proto/encode.go

@@ -1075,10 +1075,17 @@ func (o *Buffer) enc_map(p *Properties, base structPointer) error {
 
 func (o *Buffer) enc_exts(p *Properties, base structPointer) error {
 	exts := structPointer_Extensions(base, p.field)
-	if err := encodeExtensions(exts); err != nil {
+
+	v, mu := exts.extensionsRead()
+	if v == nil {
+		return nil
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if err := encodeExtensionsMap(v); err != nil {
 		return err
 	}
-	v, _ := exts.extensionsRead()
 
 	return o.enc_map_body(v)
 }

vendor/github.com/golang/protobuf/proto/extensions.go

@@ -154,6 +154,7 @@ type ExtensionDesc struct {
 	Field         int32       // field number
 	Name          string      // fully-qualified name of extension, for text formatting
 	Tag           string      // protobuf tag style
+	Filename      string      // name of the file in which the extension is defined
 }
 
 func (ed *ExtensionDesc) repeated() bool {

vendor/github.com/golang/protobuf/proto/text_parser.go

@@ -592,7 +592,11 @@ func (p *textParser) readStruct(sv reflect.Value, terminator string) error {
 			props = oop.Prop
 			nv := reflect.New(oop.Type.Elem())
 			dst = nv.Elem().Field(0)
-			sv.Field(oop.Field).Set(nv)
+			field := sv.Field(oop.Field)
+			if !field.IsNil() {
+				return p.errorf("field '%s' would overwrite already parsed oneof '%s'", name, sv.Type().Field(oop.Field).Name)
+			}
+			field.Set(nv)
 		}
 		if !dst.IsValid() {
 			return p.errorf("unknown field name %q in %v", name, st)