Fix Stdio->Stdin typo and missing external.

sdk/lib/io/stdio.dart

Index: sdk/lib/io/stdio.dart
diff --git a/sdk/lib/io/stdio.dart b/sdk/lib/io/stdio.dart
index ee8569c0148442282e7772fbfcb3941727d6544c..31a5c003bb9e82d88ac9cc19585583c35e1d7196 100644
--- a/sdk/lib/io/stdio.dart
+++ b/sdk/lib/io/stdio.dart
@@ -103,7 +103,7 @@ class Stdin extends _StdStream {
    *
    * If at end of file, -1 is returned.
    */
-  int readByteSync();
+  external int readByteSync();
 }
 
 
@@ -198,6 +198,6 @@ StdioType stdioType(object) {
 
 class _StdIOUtils {
   external static IOSink _getStdioOutputStream(int fd);
-  external static Stdio _getStdioInputStream();
+  external static Stdin _getStdioInputStream();
   external static int _socketType(nativeSocket);
 }