RSM

........S. [ZBXNEXT-4108] use proper functions for multiple updates

Use the DBbegin_multiple_update() DBend_multiple_update()
functions for upgrading multiple lines with different conditions.
This make things much simpler for updating event and problems
with multiple conditions (like trigger id, objectid and type etc..).
Tested with randomly generated events and problems for
multiple item and triggers, both for triggers and internal events.

Suggested by Andris Z.