- added bug against maps

SVN=124977

test/bugs/bug058.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
+
+type Box struct {};
+var m map[string] *Box;
+  
+func main() {
+  m["foo"] = nil;
+}
+
+/*
+bug058.go:9: illegal types for operand: INDEX
+	(MAP[<string>*STRING]*<Box>{})
+	(<string>*STRING)
+*/