Get rid of all the library tags.

lib/src/sha256.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 crypto.sha256;
-
 import 'dart:convert';
 import 'dart:typed_data';
 
 import 'digest.dart';
 import 'hash.dart';
 import 'hash_sink.dart';
 import 'utils.dart';
 
 /// An instance of [SHA256].
 ///
@@ skipping 118 matching lines @@
     digest[0] = add32(a, digest[0]);
     digest[1] = add32(b, digest[1]);
     digest[2] = add32(c, digest[2]);
     digest[3] = add32(d, digest[3]);
     digest[4] = add32(e, digest[4]);
     digest[5] = add32(f, digest[5]);
     digest[6] = add32(g, digest[6]);
     digest[7] = add32(h, digest[7]);
   }
 }