Reapply "Make Comparable generic."

sdk/lib/core/num.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.
 
 part of dart.core;
 
 /**
  * All numbers in dart are instances of [num].
  */
-abstract class num implements Comparable {
+abstract class num implements Comparable<num> {
   /** Addition operator. */
   num operator +(num other);
 
   /** Subtraction operator. */
   num operator -(num other);
 
   /** Multiplication operator. */
   num operator *(num other);
 
   /** Euclidean modulo operator. */
@@ skipping 101 matching lines @@
    * Converts [this] to a string representation with [precision] significant
    * digits.
    *
    * The parameter [precision] must be an integer satisfying:
    * [:1 <= precision <= 21:].
    */
   String toStringAsPrecision(int precision);
 
 
 }