Add the beginnings of a Dart wrapper for libarchive.

utils/archive/archive.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * The primary library file for the archive library. This is the only file that
+ * should be imported by clients.
+ */
+#library("archive");
+
+#import("reader.dart", prefix: "reader");
+
+// TODO(nweiz): Remove this when 3071 is fixed.
+/** An error raised by the archive library. */
+interface ArchiveException {
+  /** A description of the error that occurred. */   
+  final String message;
+
+  /** The error code for the error, or null. */
+  final int errno;
+}
+
+// TODO(nweiz): Remove this when 3071 is fixed.
+/** See [reader.ArchiveReader]. */
+class ArchiveReader extends reader.ArchiveReader {}