(be)(req|resp).body

[Nils Goroll]

Additional notes from IRC discussion with phk

* we also want

	set (be)(req|resp).body += "...";

  to append. This may help save workspace

* Setting the body should clear Content-Encoding
  (can be un-done for instance when a vmod injects compressed data)

* Whatever we set the body to should need to go though the (fetch) pipeline
  to get gzip/esi Processing