Disable overzealous autoloading

Due to how class_exists() works in PHP, if an auto-loader has been specified, calling this function will trigger the auto-loader and it will try to load the class in question (see http://www.php.net/manual/en/function.class-exists.php )

This is very annoying behavior when you have more than one code-base interacting with each other and one side defines an auto-loader.