checksrc.whitelist: remove fopen() uses

      150 Opening ASCII mode data connection for [file] (0.0.0.0,0) (545 bytes)

   * no_proxy=domain1.dom,host.domain2.dom

     Default values are (0,0) initialized by calloc.

  file = fopen(name, "r"); /* VMS */

    return fopen(file, "r"); /* VMS */

    return fopen(file, "r", "rfm=stmlf", "ctx=stm");

    curl_memlog("FILE %s:%d fopen(\"%s\",\"%s\") = %p\n",

           a URL as file://localhost//foo must be valid as well, to refer to

  const char atom_specials[] = "(){ %*]";