Move parseInt parseDouble to int/double classes as a static method.

lib/core/int.dart

 // Copyright (c) 2011, 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.
 
 // Dart core library.
 
 abstract class int implements num {
   // Bit-operations.
   int operator &(int other);
   int operator |(int other);
   int operator ^(int other);
   int operator ~();
   int operator <<(int shiftAmount);
   int operator >>(int shiftAmount);
 
   // Testers.
   bool isEven();
   bool isOdd();
 
   // Specializations of super-interface.
   int operator -();
   int abs();
   int round();
   int floor();
   int ceil();
   int truncate();
+  /**
+   * Returns a representation of this [int] value.
+   *
+   * It should always be the case that if 'i' is an [int] value, then
+   * [:i == int.parse(i.toString())].
+   */
+  String toString();
+
+  /**
+   * Parse [source] as an integer literal and return its value.
+   *
+   * Accepts "0x" prefix for hexadecimal numbers, otherwise defaults
+   * to base-10.
+   * Throws a [FormatException] if [source] is not a valid integer literal.
+   */
+  external static int parse(String source);
 }