Document that we are being chunking in our

content passing, as compared to simply spooling
all the content in until clen == 0. Also, we
need to cleanup the brigade after each pass.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/fcgi-proxy-dev@376346 13f79535-47bb-0310-9956-ffa450edef68