Merge attribute handling from request and response to commen code.

packages/ipp/enum.go

@@ -21,9 +21,14 @@ func NewEnum(name string, value int32) *enum {
 	return e
 }
 
+func (e enum) Name() string {
+	return e.name
+}
+
 func (e enum) String() string {
 	return e.name + ":" + fmt.Sprint(e.value)
 }
+
 func (e *enum) valueTag() tag {
 	return enumValueTag
 }