backend type in log_line_prefix?

Attached is a demo patch that adds a placeholder %b for log_line_prefix 
(not in the default setting) that contains the backend type, the same 
that you see in pg_stat_activity and in the ps status.  I would have 
found this occasionally useful when analyzing logs, especially if you 
have a lot of background workers active.  Thoughts?

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services