Zabbix

........S. [ZBX-27453] fixed average trend calculation to avoid producing inf values when dealing with DBL_MAX input; updated timeleft() function to return DBL_MAX when threshold cannot be reached and history approaches DBL_MAX

Merge in ZBX/zabbix from feature/ZBX-27453-7.5-2 to master

* commit '7c5961ab1b25e80f5e198e609159365c226aba47': (89 commits)
  ........S. [ZBX-27453] fixed overflow handling
  ........S. [ZBX-27453] removed ns from the test
  ........S. [ZBX-27453] reverted test removal
  ........S. [ZBX-27453] removed test with ns precision
  ........S. [ZBX-27453] added one more minor comment fix to integration test
  ........S. [ZBX-27453] added minor comment fixes to integration test
  ........S. [ZBX-27453] updated Changelog
  ........S. [ZBX-27453] added tests with ns difference
  ........S. [ZBX-27453] added test to directly cover the scenario where val_now below threshold and slope rising (issue B)
  ........S. [ZBX-27453] applied proposed patch
  ........S. [ZBX-27453] added more test cases
  ........S. [ZBX-27453] fixed the same issue for forecast
  ........S. [ZBX-27453] updated prediction to avoid producing -1 when dealing with DBL_MAX
  ........S. [ZBX-27453] updated zbx_regression() function to check for error earlier
  ........S. [ZBX-27453] added test that expects infinitely small timeleft()
  ........S. [ZBX-27453] reverted updated timeleft() calculation to avoid NaNs
  ........S. [ZBX-27453] revert updated timeleft() calculation to produce DBL_MAX for input arguments approaching infinity
  ........S. [ZBX-27453] updated timeleft() calculation to produce DBL_MAX for input arguments approaching infinity
  ........S. [ZBX-27453] updated timeleft() calculation to avoid NaNs
  ........S. [ZBX-27453] added Evaluate timeleft(#3,1.7976931348623158e+308,logarithmic) test
  ...