Description:
------------
When resolving MX records with the dns_get_record function, getting the raw record data isn't supported for some reason.

Test script:
---------------
<?php
echo ("Normal:\n");
var_dump(dns_get_record('daniil.it', DNS_MX, $auth, $add, false));
var_dump($auth, $add);

echo ("\nRaw:\n");
var_dump(dns_get_record('daniil.it', DNS_MX, $auth, $add, true));
var_dump($auth, $add)

Expected result:
----------------
Normal:
array(1) {
  [0]=>
  array(6) {
    ["host"]=>
    string(9) "daniil.it"
    ["class"]=>
    string(2) "IN"
    ["ttl"]=>
    int(300)
    ["type"]=>
    string(2) "MX"
    ["pri"]=>
    int(10)
    ["target"]=>
    string(13) "mx.yandex.net"
  }
}
NULL
NULL

Raw:
array(1) {
  [0]=>
  array(6) {
    ["host"]=>
    string(9) "daniil.it"
    ["class"]=>
    string(2) "IN"
    ["ttl"]=>
    int(300)
    ["type"]=>
    int(16384)
    ["data"]=>
    string(X) "binary data representing MX record"
  }
}
NULL
NUL

Actual result:
--------------
Normal:
array(1) {
  [0]=>
  array(6) {
    ["host"]=>
    string(9) "daniil.it"
    ["class"]=>
    string(2) "IN"
    ["ttl"]=>
    int(300)
    ["type"]=>
    string(2) "MX"
    ["pri"]=>
    int(10)
    ["target"]=>
    string(13) "mx.yandex.net"
  }
}
NULL
NULL

Raw:
array(0) {
}
NULL
NUL