Fix a bug in the APR_MODE_EXHAUSTIVE mode for the core input filter.

This patch changes nothing outside of that mode.

Also, why do we ever call apr_brigade_length() in the core? This doesn't
seem right to me, so here's a comment above the other call.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93736 13f79535-47bb-0310-9956-ffa450edef68