error-notes

[Doug MacEachern <do...@pobox.com>]

I gave this a +1, I think it's a great feature for ErrorDocuments, etc.
But, consider a module that calls ap_log_rerror, with a bit of APLOG_INFO,
APLOG_DEBUG, then hits an actual problem, APLOG_ERROR, then return
SERVER_ERROR.
If the ErrorDocument wants to be more informative, error-notes does little
good, as it will contain the first ap_log_rerror() message, which was just
INFO.
I think ap_log_rerror() should always override what's already in
error-notes or only set error-notes if the log mask is APLOG_ERROR.  Thoughts?

-Doug