Split scannerlib.dart into several libraries.

pkg/compiler/lib/src/diagnostics/source_span.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 dart2js.diagnostics.source_span;
 
-import '../scanner/scannerlib.dart' show
+import '../scanner/token.dart' show
     Token;
 import '../tree/tree.dart' show
     Node;
 import 'spannable.dart' show
     Spannable;
 
 class SourceSpan implements Spannable {
   final Uri uri;
   final int begin;
   final int end;
@@ skipping 24 matching lines @@
   bool operator ==(other) {
     if (identical(this, other)) return true;
     if (other is! SourceSpan) return false;
     return uri == other.uri &&
            begin == other.begin &&
            end == other.end;
   }
 
   String toString() => 'SourceSpan($uri, $begin, $end)';
 }