Bug cleanup: unify on allowing radices from 2 to 36 in

lib/core/num.dart

Index: lib/core/num.dart
diff --git a/lib/core/num.dart b/lib/core/num.dart
index 3203b05e3bb0f83c5d5ab662e1a4861a3a42dfe7..f8d5842f8856d4c60e3e74e9c9ab1944fc7339ad 100644
--- a/lib/core/num.dart
+++ b/lib/core/num.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -40,5 +40,16 @@ abstract class num implements Comparable, Hashable {
   String toStringAsFixed(int fractionDigits);
   String toStringAsExponential(int fractionDigits);
   String toStringAsPrecision(int precision);
+
+  /**
+   * Converts a [num] to a string representation in the given [radix].
+   *
+   * The [num] in converted to an [int] using [toInt]. That [int] is
+   * then converted to a string representation with the given
+   * [radix]. In the string representation, lower-case letters are
+   * used for digits above '9'.
+   *
+   * The [radix] argument must be an integer between 2 and 36.
+   */
   String toRadixString(int radix);
 }