Log TOS and Netfilter marks set by Squid

Log TOS and Netfilter marks set by Squid

This patch add new logformat codes to log TOS/DSCP values and netfilter marks
for client and server connections. If multiple outgoing connections were used,
the last used connection value logged.
The values printed in hexadecimal form.
The logformat codes are:
   %>tos    Client connection tos mark set by Squid
   %<tos    Server connection tos mark set by Squid
   %>nfmark Client connection netfilter mark set by Squid
   %<nfmark Server connection netfilter mark set by Squid

This patch also modify qos related code to set Comm::Connection::nfmark and
Comm::Connection::tos members in Ip::Qos::setSockNfmark and Ip::Qos::setSockTos
methods. The Comm::Connection members are now set only if the tos and nfmark
set successfuly.

This is a Measurement Factory project