update error() to use ... at call site.
thanks to ztomic@.

R=rsc
CC=golang-dev, ztomic
http://codereview.appspot.com/2295042
diff --git a/proto/text_parser.go b/proto/text_parser.go
index 4c0166f..4076ebb 100644
--- a/proto/text_parser.go
+++ b/proto/text_parser.go
@@ -89,7 +89,7 @@
 }
 
 func (p *textParser) error(format string, a ...interface{}) *ParseError {
-	pe := &ParseError{fmt.Sprintf(format, a), p.cur.line, p.cur.offset}
+	pe := &ParseError{fmt.Sprintf(format, a...), p.cur.line, p.cur.offset}
 	p.cur.err = pe
 	p.done = true
 	return pe