Zabbix

A.FGI..PS. [ZBXNEXT-1263] added encryption support for communications between Zabbix components (server, proxies, agents and command-line utilities)

Before this change:
   - network communication between Zabbix components was not encrypted,
   - when active proxy connected to server, proxy details were searched in database.
After this change:
   - mbed TLS (PolarSSL), GnuTLS or OpenSSL can be used for TLS support,
   - new configuration parameters added for TLS support to zabbix_server.conf,
     zabbix_proxy.conf, zabbix_agentd.conf, zabbix_agentd.win.conf,
   - new commandline options added for TLS support to 'zabbix_get',
     'zabbix sender' utilities,
   - new database table columns added for TLS support,
   - RSA certificates or PSK can be configured and used for TLS per host/proxy.
   - configuration cache modified to store TLS parameters,
   - connection type management added to specify encryption on outgoing
     connections and to enforce policy for incoming connections per host/proxy,
   - improved efficiency for outgoing connections - now Zabbix protocol header,
     data length and data up to 16 KB is passed to OS in one operation,
   - core dumps are disabled,
   - adjusted layout of "--help" messages to fit on 80-column terminals,
   - when active proxy connects to server, proxy details are searched in
     configuration cache.