zabbix: add sqlite3 support

This change makes it possible to build zabbix with sqlite3 support.

Attention:
By selecting "SQLite" as "Database Software" you are not able
to build the zabbix-server and zabbix-server-frontend package anymore.
This database is not supported for this service.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>