Check url as 'A' type record in DNS instead 'MX'

Example,
```
checkdnsrr('www.laravel.com'); // false
but
checkdnsrr('www.laravel.com', 'A'); //true
```
Added test for check A type DNS
Merge pull request #6026 from vlastv/patch-1

[5.0] Check url as 'A' type record in DNS instead 'MX'