[DOC] added documentation for "option tcplog" to "use_backend"

- options tcplog, tcpsplice and transparent have been documented.
- keywords "srvtimeout", "timeout queue", "timeout server" and
  "timeout tarpit" have been documented
- keywords "transparent" and "use_backend" have been documented

Only "server", "source" and "stats *" remain undocumented
1 file changed