[PATCH] 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

I must note that the setsockopt(...,IPPROTO_IP, IP_TOS...) system call
we are using to set tos value may not set the configured value. It can
set only values which are multiple of 4. In this case we log wrong
value, the configured not the value is set.

To get the real value we must modify the Ip::Qos::setSockTos method to
set the TOS and then read it again from socket to see which value is
used. However this is means one more system call to set the tos value.

Regards,
   Christos