Allow custom flash_message messages

[Sama34]

With the following modification plug-in aturhos would be able to add custom alerts as follows.

$plugins->add_hook('admin_page_output_header', 'helloworld_admin_page_output_header');

function helloworld_admin_page_output_header()
{
    global $helloworld, $page;

    $message = 'Hello World! is up-to-date. Congratulations!';
    $type = 'success';

    if($helloworld->requires_update == true)
    {
        $message = 'Hello World! plug-in needs to be updated. Please click here to update the plug-in.';
        $type = 'error';
    }

    $page->extra_messages['helloworld'] = array('message' => $message, 'type' => $type);
}

Refference: http://community.mybb.com/thread-118099.html