Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

pkg/compiler/lib/src/hash/sha1.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.
 
 /**
  * SHA-1.
  * Ripped from package:crypto.
  */
 library sha1;
 
@@ skipping 357 matching lines @@
       int y = bytes[i + 1];
       out[j++] = lookup.codeUnitAt(x >> 2);
       out[j++] = lookup.codeUnitAt(((x << 4) | (y >> 4)) & 0x3F);
       out[j++] = lookup.codeUnitAt((y << 2) & 0x3F);
       out[j++] = PAD;
     }
 
     return new String.fromCharCodes(out);
   }
 }