Logging circuit-id

[Sean McMurray]

I would like my dhcpd logs to include circuit-id.
I have tried to use log() directives in my conf file, but nothing I have 
tried works.

Here is an example of a configuration I have included in a subnet:

   log(info, concat(
     " Mac: ",binary-to-ascii(16, 8, ":", substring(hardware,1, 6))
     ," IP: ",binary-to-ascii (10, 8, ".", leased-address)
     ,"Circuit: ",option agent.circuit-id
   ));


Standard logging is working fine to record DHCPDISCOVER, DHCPOFFER, etc. 
I just can't get custom entries to show up in the log.