Move interpretation of Content-Length to cache_http.c since HTTP/2
will also use it.
Set the protocol-specific body status in http_conn for both req and resp.
Use the protocol specific info to determine precense of request body.
Be consistent about bo-> vs bo.
Add asserts
Use the HTTP/1 VFP's for fetching the req.body
Eliminate a unused REQ_BODY state
Remove leftovers from ESI handling that now happens in req_fsm
Set X-F-F early enough that it's present if we head directly to synth{}