Correct the ProxyIOBufferSize docs to match the code. Add a note about the AJP
behaviour as per http://www.mail-archive.com/dev@httpd.apache.org/msg41843.html.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1476655 13f79535-47bb-0310-9956-ffa450edef68