1.1.5 -> 1.1.6
  * added reqdeny / reqallow rules
  * added HTTP 400 and 403 responses
  * chain regex in a list
  * reply 502 when no server is available
1.1.6 -> 1.1.7
  * implement global logging
  * have a single log function
  * add x-forwarded-for
  * log http requests on demand, and destination server name
1.1.7 -> 1.1.8
  - log destination server IP
  - handle parametrable HTTP health-checks replies
  - differentiate http headers and http uris
  - support keep-alive