test: add another test that gccgo failed to compile

Change-Id: Ife9e019063473bb0a976cfef4b6e78d951fcb09e
Reviewed-on: https://go-review.googlesource.com/17081
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

test/fixedbugs/bug496.go

+// compile
+
+// Copyright 2015 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 used to give an error:
+// <built-in>: error: redefinition of ‘s$F$hash’
+// <built-in>: note: previous definition of ‘s$F$hash’ was here
+// <built-in>: error: redefinition of ‘s$F$equal’
+// <built-in>: note: previous definition of ‘s$F$equal’ was here
+
+package p
+
+type T1 int
+
+func (t T1) F() {
+	type s struct {
+		f string
+	}
+}
+
+type T2 int
+
+func (t T2) F() {
+	type s struct {
+		f string
+	}
+}