test: Actually run bug296.

R=rsc
CC=golang-dev
https://golang.org/cl/2156045

test/fixedbugs/bug296.go

@@ -1,3 +1,9 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package main
 
 type I interface {