The attached patch implements agent side filtering of event log events on the 'event source' and 'event type'.

For this functionality the Item key eventlog parameter syntax is extended to allow two extra optional parameters that enable the user to specify a filter expression for the event source and for the event type.

New parameter syntax:

eventlog[<eventlog name>,<event value (description) filter expression>,<event source filter expression>,<event type filter expression>]

This change can greatly reduce the number of events that is sent to the Zabbix server, especially when monitoring just one application or just the error events.