Added average_latency_cmk and average_latency_real_time
columns, always containing zero.
Added average_latency_generic column, containing the average
latency of all active host/service checks.
Added core_pid column as an alias for nagios_pid.
Added has_event_handlers column.
Added helper_usage_generic, helper_usage_cmk, and
helper_usage_real_time columns, always containing zero.
Added livestatus_overflows and livestatus_overflows_rate
columns. The NEB queues accepted connections, so we never have overflows here.
Nevertheless, we provide these columns for consistency with CMC, and they always
contain zero.
Removed livecheck_overflows and livecheck_overflows_rate
columns from both NEB and CMC. They were unused for more than 6 years, they
never really worked well, and simply contain zero for ages. To reduce confusion,
those columns are gone now.
