* Added a 'USERS.LOCAL_AUTH' field to the database.
* Added a 'USERS.PAM_SERVICE' field to the database.
* Added an index on 'STATIONS.IPV4_ADDRESS' to the database.
* Incremented the database version to 262.
* Added 'RDUser::localAuthentication()',
'RDUser::setLocalAuthentication()', 'RDUser::pamService()' and
'RDUser::setPamService()' methods in 'lib/rduser.cpp' and
'lib/rduser.h'.
* Added 'PAM Service' and 'Authenticate This User Locally' controls
to the Edit User dialog in 'rdadmin/edit_user.cpp' and
'rdadmin/edit_user.h'.
* Added a PAM service configuration in 'conf/rivendell.pam'.
