gc: another width test

R=ken2
CC=golang-dev
https://golang.org/cl/4808057

test/fixedbugs/bug361.go

+// $G $D/$F.go || echo BUG: bug360
+
+// Copyright 2011 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.
+
+// issue 1908
+// unreasonable width used to be internal fatal error
+
+package test
+
+func main() {
+	buf := [1<<30]byte{}
+	_ = buf[:]
+}