Avoid use of deprecated __autoload function

Summary:
The __autoload() magic method has been deprecated in PHP 7.2.

Fixes T99.

Test Plan:

require 'includes/autoload.php';
$ship = new Ship;

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T99

Differential Revision: https://code.zed.dereckson.be/D11