Add Zabbix version storing. Make compatible with 2.4
(minor changes in commits 340c5c13a8407367b8de6d7fe579fe10eefafb78, 45313506fb8ff3db3a43ce66742c68f7a9849510 and 9f98c4b26231ec20a80d44c6824d4fcd6514316b from https://github.com/sladewig/zabbix)