Don't allow pre-release versions of the max in "<" constraints.

sdk/lib/_internal/pub/test/version_solver_test.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.
 
 library pub_upgrade_test;
 
 import 'dart:async';
 
 import 'package:unittest/unittest.dart';
 
@@ skipping 875 matching lines @@
     'myapp from root': '0.0.0',
     'a': '1.0.0'
   });
 
   testResolve('use latest allowed prerelease if no stable versions match', {
     'myapp 0.0.0': {
       'a': '<2.0.0'
     },
     'a 1.0.0-dev': {},
     'a 1.1.0-dev': {},
-    'a 2.0.0-dev': {},
+    'a 1.9.0-dev': {},
     'a 3.0.0': {}
   }, result: {
     'myapp from root': '0.0.0',
-    'a': '2.0.0-dev'
+    'a': '1.9.0-dev'
   });
 
   testResolve('use an earlier stable version on a < constraint', {
     'myapp 0.0.0': {
       'a': '<2.0.0'
     },
     'a 1.0.0': {},
     'a 1.1.0': {},
     'a 2.0.0-dev': {},
     'a 2.0.0': {}
@@ skipping 599 matching lines @@
   }
 
   var source = "mock1";
   if (match[7] != null) {
     source = match[7];
     if (source == "root") source = null;
   }
 
   return new PackageId(name, source, parsedVersion, description);
 }