input filtering changes:

  get dechunking working
  verify that infrastructure for input filters works
    (use existing AddInputFilter directive)

Unlike with my previous patch, ap_get_client_block() saves state between
calls in the core's per-request dir config.

Unlike with my previous patch, HTTP_IN keeps a count of remaining bytes
in the conn_rec.  Code that needs to prod it to deliver a certain amount
of request body plays with conn_rec->remain directly.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86613 13f79535-47bb-0310-9956-ffa450edef68