Use FormatMessageW for Windows error messages to handle internationalized messages correctly.

runtime/bin/platform.h

Index: runtime/bin/platform.h
diff --git a/runtime/bin/platform.h b/runtime/bin/platform.h
index 38cafbe2ad84b3953e005bb8ae25320a5feb3f8a..9ee217235b2db407d863dba1beae3a91688329be 100644
--- a/runtime/bin/platform.h
+++ b/runtime/bin/platform.h
@@ -20,10 +20,6 @@ class Platform {
   // deallocated by the caller.
   static const char* OperatingSystem();
 
-  // Returns a string representation of an error code. The returned
-  // string must be deallocated by the caller.
-  static char* StrError(int error_code);
-
   // Extracts the local hostname.
   static bool LocalHostname(char* buffer, intptr_t buffer_length);