test: add test case that failed when built with gccgo

Change-Id: Ie7512cc27436cde53b58686b32a0389849a365e4
Reviewed-on: https://go-review.googlesource.com/33249
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

test/fixedbugs/bug499.go

+// run
+
+// Copyright 2016 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.
+
+// Gccgo got confused when a type was used both for a map bucket type
+// and for a map key type.
+
+package main
+
+func main() {
+	_ = make(map[byte]byte)
+	_ = make(map[[8]byte]chan struct{})
+}