PHP 5.3 deprecated & fix

[Simkea]

Problem:
session_unregister is deprecated in controller.php

Fix:
Row 75 replace:
session_unregister('ck_send_once'.$ckform->id);
with:
unset($_SESSION['ck_send_once'.$ckform->id]);

Row 81 the same as:
unset($_SESSION['securimage_code_value']);

best regards