Fix Stdio->Stdin typo and missing external.

sdk/lib/io/stdio.dart

 // Copyright (c) 2013, 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 dart.io;
 
 const int _STDIO_HANDLE_TYPE_TERMINAL = 0;
 const int _STDIO_HANDLE_TYPE_PIPE = 1;
 const int _STDIO_HANDLE_TYPE_FILE = 2;
 const int _STDIO_HANDLE_TYPE_SOCKET = 3;
@@ skipping 85 matching lines @@
     if (empty) return null;
     return line.toString();
   }
 
   /**
    * Synchronously read a byte from stdin. This call will block until a byte is
    * available.
    *
    * If at end of file, -1 is returned.
    */
-  int readByteSync();
+  external int readByteSync();
 }
 
 
 class _StdSink implements IOSink {
   final IOSink _sink;
 
   _StdSink(IOSink this._sink);
 
   Encoding get encoding => _sink.encoding;
   void set encoding(Encoding encoding) {
@@ skipping 74 matching lines @@
     } catch (e) {
       // Only the interface implemented, _sink not available.
     }
   }
   return StdioType.OTHER;
 }
 
 
 class _StdIOUtils {
   external static IOSink _getStdioOutputStream(int fd);
-  external static Stdio _getStdioInputStream();
+  external static Stdin _getStdioInputStream();
   external static int _socketType(nativeSocket);
 }