goprotobuf: Rename some fields for clarity.

R=r
CC=golang-dev
http://codereview.appspot.com/6576047
diff --git a/proto/text_parser.go b/proto/text_parser.go
index 1dff7cb..1f170bf 100644
--- a/proto/text_parser.go
+++ b/proto/text_parser.go
@@ -374,7 +374,7 @@
 // Returns the index in the struct for the named field, as well as the parsed tag properties.
 func structFieldByName(st reflect.Type, name string) (int, *Properties, bool) {
 	sprops := GetProperties(st)
-	i, ok := sprops.origNames[name]
+	i, ok := sprops.decoderOrigNames[name]
 	if ok {
 		return i, sprops.Prop[i], true
 	}