handle prefix of "_"
handle "_" prefix in db error messages
Merge remote-tracking branch 'origin/master' into 1.4.6

Conflicts:
	zp-core/utilities/backup_restore.php

	modified:   zp-core/functions-db-MySQL.php
	modified:   zp-core/functions-db-MySQLi.php
	modified:   zp-core/functions-db_PDO.php
	modified:   zp-core/utilities/backup_restore.php