goprotobuf: Be more liberal in text format string parsing.

Also, a minor style tweak in CompactTextString.

R=r
CC=golang-dev
http://codereview.appspot.com/5876069
diff --git a/proto/text.go b/proto/text.go
index ae0453c..9cd7b69 100644
--- a/proto/text.go
+++ b/proto/text.go
@@ -463,7 +463,7 @@
 
 // CompactTextString is the same as CompactText, but returns the string directly.
 func CompactTextString(pb interface{}) string {
-	buf := new(bytes.Buffer)
-	marshalText(buf, pb, true)
+	var buf bytes.Buffer
+	marshalText(&buf, pb, true)
 	return buf.String()
 }