Update deprecated constructors.

I think we should update the deprecated constructors. Though this deprecation was recently introduced it seems like an easy update. Managed to list 4 of them using a compatibility checker.

File: /home/lz/sites/moneysuite/ms_core/gateways/ms_paypal_wps/includes/ms_paypal_wps_class.php
 Line 14: PHP 4 constructors are now deprecated
    function ms_paypal_wps_class($ipn_vars = NULL)
    {
    }


File: /home/lz/sites/moneysuite/ms_core/gateways/ms_ibis/Merchant.php
 Line 51: PHP 4 constructors are now deprecated
    function Merchant($url, $keystore, $keystorepassword, $verbose = 0)
    {
    }


File: /home/lz/sites/moneysuite/ms_core/gateways/ms_realex/ms_realex.class.php
 Line 19: PHP 4 constructors are now deprecated
    function RealexRemote($url, $xml)
    {
    }


File: /home/lz/sites/moneysuite/ms_affiliates/includes/ms_paypal_wps_class.php
 Line 18: PHP 4 constructors are now deprecated
    function ms_paypal_wps_class($ipn_vars = NULL)
    {
    }

Draft:

  function __construct($ipn_vars = NULL) {
    $this->ipnLink = (isset($ipn_vars['test_ipn']) AND $ipn_vars['test_ipn']) ? 'https://www.sandbox.paypal.com/cgi-bin/webscr' : 'https://www.paypal.com/cgi-bin/webscr';
    $this->ipn_vars = $ipn_vars;
    $this->lastError = '';
    $this->ipnResult = '';
  }  
 
  function ms_paypal_wps_class($ipn_vars = NULL) {
    self::__construct();  
  }

Ref:
https://cweiske.de/tagebuch/php4-constructors-php7.htm