avoid using GetTempFileName in a way it's documented to not work on windows

		      myf MyFlags __attribute__((unused)))

{

  File file= -1;

#ifdef __WIN__

  TCHAR path_buf[MAX_PATH-14];

#endif

  DBUG_ENTER("create_temp_file");

  DBUG_PRINT("enter", ("dir: %s, prefix: %s", dir, prefix));

#if defined (__WIN__)

   /*

     Use GetTempPath to determine path for temporary files.

     This is because the documentation for GetTempFileName 

     has the following to say about this parameter:

     "If this parameter is NULL, the function fails."

   */

   if (!dir)

   {

     if(GetTempPath(sizeof(path_buf), path_buf) > 0) 

       dir = path_buf;

   }

   /*

     Use GetTempFileName to generate a unique filename, create

     the file and release it's handle