This has been introduced in 2.5, so when upgrading from previous versions
make sure we set a default value. Otherwise, we get a notice about it
being undefined when we try to use it (and we always try to use it!).
They now share most of the code again, this time via subclassing, and they
share some code with enrol/ldap. They have also gained some features and a few
fixes.
As authentication and enrolment plugins now have a version number, the LDAP
version number setting was "shadowed" by the plugin version number. So we
rename the LDAP setting name to ldap_version, et voila!
Eloy Lafuente (stronk7)