corrected bug187; dropped on the floor somehow

R=austin
DELTA=23  (23 added, 0 deleted, 0 changed)
OCL=34340
CL=34346

test/fixedbugs/bug187.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// 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 "os"
+
+func main() {
+	// This bug doesn't arise with [...]int, or []interface{} or [3]interface{}.
+	a := [...]interface{} { 1, 2, 3 };
+	n := 1;
+	bug := false;
+	for _, v := range a {
+		if v.(int) != n {
+			println("BUG:", n, v.(int));
+			os.Exit(0);
+		}
+		n++;
+	}
+}