Update intl to new import syntax

pkg/intl/lib/src/date_format_field.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.
 
+part of intl;
+
 /**
  * This is a private class internal to DateFormat which is used for formatting
  * particular fields in a template. e.g. if the format is hh:mm:ss then the
  * fields would be "hh", ":", "mm", ":", and "ss". Each type of field knows
  * how to format that portion of a date.
  */
 abstract class _DateFormatField {
   /** The format string that defines us, e.g. "hh" */
   String pattern;
 
@@ skipping 380 matching lines @@
     var basicString = toBePrinted.toString();
     if (basicString.length >= width) return basicString;
     var buffer = new StringBuffer();
     for (var i = 0; i < width - basicString.length; i++) {
       buffer.add('0');
      }
     buffer.add(basicString);
     return buffer.toString();
   }
 }