Update dart:io to convert strings between UTF8 and current code page

runtime/bin/platform_macos.cc

 // 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.
 
 #include "bin/platform.h"
 
 #include <crt_externs.h>
 #include <signal.h>
 #include <string.h>
 #include <unistd.h>
@@ skipping 49 matching lines @@
   while (*(tmp++) != NULL) i++;
   *count = i;
   char** result = new char*[i];
   for (intptr_t current = 0; current < i; current++) {
     result[current] = environ[current];
   }
   return result;
 }
 
 
+void Platform::FreeEnvironment(char** env, intptr_t count) {
+  delete[] env;
+}
+
+
 char* Platform::StrError(int error_code) {
   static const int kBufferSize = 1024;
   char* error = static_cast<char*>(malloc(kBufferSize));
   error[0] = '\0';
   strerror_r(error_code, error, kBufferSize);
   return error;
 }