'remove-self' => array( removable groups from self )
)
+'UserRights::showEditUserGroupsForm': called right before the form to edit group memberships at Special:UserRights is shown
+&$user: User or UserRightsProxy you're editing
+&$addable: Array of groups you can add the user into
+&$removable: Array of groups that you can remove the user from
+
'UserRetrieveNewTalks': called when retrieving "You have new messages!" message(s)
$user: user retrieving new talks messages
$talks: array of new talks page(s)