Zabbix

.......PS. [ZBX-15942] changed proxy to send timestamps of empty historical values to server, so throttled items are not listed in administration/queue

* commit '90508b8d0f789c20c02e965815bde3e3e4c526e9':
  .......... [ZBX-15942] updated changelog
  .......... [ZBX-15942] added changelog entry
  .......P.. [ZBX-15942] removed logically dead code
  .......P.. [ZBX-15942] improved last clock setting by processing batch of data from last to first, thus ensuring that last clock is always set
  .......P.. [ZBX-15942] send clock with novalue updates to calculate queue correctly when old data is received; update clock to the latest novalue check
  .......P.. [ZBX-15942] refactored proxy history retrieval
  .......P.. [ZBX-15942] fixed proxy history lastid update with no records to be sent (all throttled)
  .......PS. [ZBX-15942] style fix
  .......PS. [ZBX-15942] fixed function header
  .......P.. [ZBX-15942] added check to prevent sending novalue updates for items not counted in administrator queue
  .......P.. [ZBX-15942] Added checks to proxy data sending to avoid sending duplicate novalue updates for the same item in one batch
  .......P.. [ZBX-15942] removed timestamps from proxy history for items without values/meta
  .......P.. [ZBX-15942] refactored code to avoid redundant meta check for items with no value type
  .......PS. [ZBX-15942] removed redundant passing of metadata that will never be used
  .......PS. [ZBX-15942] fixed crash in case of unsupported item without value
  .......PS. [ZBX-15942] style fix
  .......PS. [ZBX-15942] changed proxy to send timestamps of empty (throttled values) to server. Required for queue calculations

(cherry picked from commit 6b2f6efc332642fd71229f45b0a22f0670c2e73e)