add bug to capture double declaration of name in file and package block

R=rsc
DELTA=12  (12 added, 0 deleted, 0 changed)
OCL=33554
CL=33563

test/fixedbugs/bug192.go

+// errchk $G $D/$F.go
+
+// Copyright 2009 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
+
+import "fmt"
+
+var fmt int	// ERROR "redecl"

test/golden.out

@@ -168,3 +168,4 @@ bugs/bug190.go:13: invalid recursive type chan S
 bugs/bug190.go:16: invalid recursive type S
 bugs/bug190.go:15: invalid recursive type func(S) (S)
 BUG: should compile
+bugs/bug191.go succeeded with no output.