Copy expressions.dart to constructors.dart and evaluation.dart
Copy expressions.dart to constructors.dart and evaluation.dart

Based on https://codereview.chromium.org/1279613003

In preparation for https://codereview.chromium.org/1282463002

R=karlklose@google.com

Review URL: https://codereview.chromium.org//1275343002.

dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk