Move constant systems into their own libraries.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

 // Copyright (c) 2013, 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.
 
 library dart2js.ir_builder;
 
+import '../constants/constant_system.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart' show PrimitiveConstantValue;
 import '../dart_types.dart';
 import '../dart2jslib.dart';
 import '../elements/elements.dart';
 import '../io/source_information.dart';
 import '../tree/tree.dart' as ast;
 import '../closure.dart' hide ClosureScope;
 import '../universe/universe.dart' show SelectorKind;
 import 'cps_ir_nodes.dart' as ir;
@@ skipping 2642 matching lines @@
 }
 
 /// Synthetic parameter to a JavaScript factory method that takes the type
 /// argument given for the type variable [variable].
 class TypeInformationParameter implements Local {
   final TypeVariableElement variable;
   final ExecutableElement executableContext;
   TypeInformationParameter(this.variable, this.executableContext);
   String get name => variable.name;
 }