log_line_info plan

I am about to redo the patch that would allow tagging of log lines with 
info via a printf-style string.

Current plans are to call the config parameter "log_line_info" and 
implement the following escapes:

%U = user
%D = database
%T = timestamp
%P = pid
%L = session log line number
%C = sessionid cookie (hex encoded session start time + pid)
%S = session start timestamp
%I = Command Tag (e.g. "CREATE TABLE")

Any comments or suggestions before I start?

cheers

andrew