Move core and coreimpl from corelib/ to lib/core and lib/coreimpl.

corelib/src/double.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.
-
-interface double extends num {
-  static final double NAN = 0.0 / 0.0;
-  static final double INFINITY = 1.0 / 0.0;
-  static final double NEGATIVE_INFINITY = -INFINITY;
-
-  // Specialization of super-interface. Double is contagious. We can therefore
-  // specialize more methods than in other num sub-interfaces.
-  double remainder(num other);
-  double operator +(num other);
-  double operator -(num other);
-  double operator *(num other);
-  double operator %(num other);
-  double operator /(num other);
-  double operator ~/(num other);
-  double operator negate();
-  double abs();
-  double round();
-  double floor();
-  double ceil();
-  double truncate();
-}