MDL-63730 lang: Merge English strings from the en_fix language pack

Significant string changes:

* withselectedusers_help, core - removing mention of 'Add a common note'
  as the option no longer exists
* considereddigitalminor and digitalminor_desc, core - more
  child-friendly wording
* configmessagingallusers, core_admin - clearer explanation
* auth_dbtype, auth_db - fixed broken link

auth/db/lang/en/auth_db.php

@@ -59,7 +59,7 @@ $string['auth_dbsybasequotinghelp'] = 'Sybase style single quote escaping - need
 $string['auth_dbsyncuserstask'] = 'Synchronise users task';
 $string['auth_dbtable'] = 'Name of the table in the database';
 $string['auth_dbtable_key'] = 'Table';
-$string['auth_dbtype'] = 'The database type (See the <a href="http://phplens.com/adodb/supported.databases.html" target="_blank">ADOdb documentation</a> for details)';
+$string['auth_dbtype'] = 'The database type (see the documentation <a href="http://adodb.org/dokuwiki/doku.php" target="_blank">ADOdb - Database Abstraction Layer for PHP</a> for details).';
 $string['auth_dbtype_key'] = 'Database';
 $string['auth_dbupdateusers'] = 'Update users';
 $string['auth_dbupdateusers_description'] = 'As well as inserting new users, update existing users.';