At the hack-athon we decided to change the way that input filters

At the hack-athon we decided to change the way that input filters
determine how much data is returned to the previous filter.  Prior to this
change, we used a field in the conn_rec to determine how much to return.
After this change, we use an argument to ap_get_brigade.  This makes it
much more obvious how things work at all levels, so that module authors
can easily determine how much data is supposed to be returned to them.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88912 13f79535-47bb-0310-9956-ffa450edef68