Bug 44757

It would be nice have the filter chain mechanism applied to stderr.
Many cgi languages emit errors on stderr, so different "stderr filters" would allow you to do different things with the stderr data..

For instance one module may log special error reports, one might spit a report back to the user visually on the dev area, one might send emails to the exact programmer who coded the site... heck one module may communicate back to the apache's scoreboard lb or an f5, and take itsself out of service...

I proposed this way back when 2.0 first came about, and I have basic patches.
(at that time mod_cgi had issues with stderr so I scrapped my patches at the time).

One other important feature is that the "posted data" also gets shipped to the stderr filters.  Then for instance the mod_cgi_bomb filter can report "for app XXXX, it causes the internal server 500.  Heres the posted data and all the env vars passed to the cgi that caused it to blow up"...

It should be noted that "log_script()" in mod_cgi.c would be the default stderr filter...  if none were assigned.

My code only works with mod_cgi.c so far.  I havent had time to get it to work with mod_cgid.c yet.