[exim] Feature requests for eximstats: Receipt time and reje…

I've got a few feature requests for eximstats. I'm not sure if this is
the right place to post them -- is there another list for that app?

1) Charting receipt time for messages. This can be calculated if the
message was logged with either +queue_time or +queue_time_overall.
eximstats already calculates the time spent on the queue as the
difference between <= and Completed log entries for a given message.
The receipt time is the difference between the QT on the Completed
logged by queue_time_overall and the calculated time.

This would be easier if exim had a +receipt_time log selector (which
would presumably put RT=nns on the <= log entry), but that's not
strictly necessary.

2) Histograms for the various rejection types. Alternatively, providing
histograms for the various regexes defined with the -pattern option
would do the trick; currently, just a total count is provided.

Thanks,
- Marc