[CONTRIB] halog: report per-server status codes, errors and response times

[CONTRIB] halog: report per-server status codes, errors and response times

It's sometimes very useful to be able to monitor a production status in real
time by comparing servers behaviours. Now halog is able to do this when called
with "-srv". It reports various fields for each server found in a log, including
statuses, total reqs, valid reqs, percent of valid reqs, average connection time,
average response time.