Reverted Libiconv on Linux. It's installed in linux by default.

Signed-off-by: Daniel (dmilith) Dettlaff <dmilith@verknowsys.com>
Fixed Zabbix build for FreeBSD hosts (No iconv available in base system of FreeBSD).

Signed-off-by: Daniel (dmilith) Dettlaff <dmilith@verknowsys.com>