LDAP Authorization: track drupal roles added and removed by ldap_authorization in user.data array

Just as authmap is used for tracking the origination of external users, its quite possible we will need to track drupal roles granted and removed by ldap_authorization module. Even if its just helpful for user support and debugging.

$user->data['ldap_authorization']['removed_roles'] = array()
$user->data['ldap_authorization']['added_roles'] = array()