Fix to dartbug.com/5170, explictly static library variables now get an appropriate error message.

lib/compiler/implementation/warnings.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.
 
 class MessageKind {
   final String template;
   const MessageKind(this.template);
 
   static const GENERIC = const MessageKind('#{1}');
 
@@ skipping 279 matching lines @@
       "Optional parameter count of patch method (#{3}) doesn't match parameter "
       "count on origin method '#{1}' (#{2}).");
 
   static const PATCH_OPTIONAL_PARAMETER_NAMED_MISMATCH = const MessageKind(
       "Optional parameters of origin and patch method '#{1}' must "
       "both be either named or positional.");
 
   static const PATCH_PARAMETER_MISMATCH = const MessageKind(
       "Patch method parameter '#{3}' doesn't match '#{2}' on origin method "
       "#{1}.");
+  
+  static const TOP_LEVEL_VARIABLE_DECLARED_STATIC = const MessageKind(
+      "Top-level variable cannot be declared static.");
 
   static const COMPILER_CRASHED = const MessageKind(
       "Error: The compiler crashed when compiling this element.");
 
   static const PLEASE_REPORT_THE_CRASH = const MessageKind('''
 The compiler is broken.
 
 When compiling the above element, the compiler crashed. It is not
 possible to tell if this is caused by a problem in your program or
 not. Regardless, the compiler should not crash.
@@ skipping 79 matching lines @@
 
 class CompileTimeConstantError extends Diagnostic {
   CompileTimeConstantError(MessageKind kind, List arguments)
     : super(kind, arguments);
 }
 
 class CompilationError extends Diagnostic {
   CompilationError(MessageKind kind, List arguments)
     : super(kind, arguments);
 }