Zabbix

.......... [ZBX-12451,ZBX-13797,ZBXNEXT-4569,ZBXNEXT-4570] merged from latest trunk; fixed conflicts in:

- create/src/schema.tmpl
- src/libs/zbxdbupgrade/dbupgrade_3050.c
- frontends/php/include/defines.inc.php
- frontends/php/tests/api_json/testHostGroup.php