win: use GetVersionExW instead of GetVersionExA

For consistency with the rest of the source code, use the wide-char
version of this API.

PR-URL: https://github.com/iojs/io.js/pull/261
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/node_os.cc

@@ -106,12 +106,12 @@ static void GetOSRelease(const FunctionCallbackInfo<Value>& args) {
     return env->ThrowErrnoException(errno, "uname");
   }
   rval = info.release;
-#else  // __MINGW32__
+#else  // Windows
   char release[256];
-  OSVERSIONINFO info;
+  OSVERSIONINFOW info;
 
   info.dwOSVersionInfoSize = sizeof(info);
-  if (GetVersionEx(&info) == 0)
+  if (GetVersionExW(&info) == 0)
     return;
 
   snprintf(release,