Clears the event log
_EventLog__Clear ( $hEventLog, $sFileName )
|$hEventLog||Handle to the event log|
|$sFileName||The name of the backup file. If the name is blank, the current event log is not backed up.|
This function fails if the event log is empty or a file already exists with the same name as $sFileName.
After this function returns, any handles that reference the cleared event log cannot be used to read the log.