[PATCH] Compliance: Dechunk incoming requests as they come in and chunk outgoing requests

Compliance: Dechunk incoming requests as they come in and chunk outgoing
requests.

The server side always chunks the request if and only if the original
request was chunked. No next hop version checks are performed.

This is the final version of the patch that is ready for previously
posted 1xx handling patch integration. I would like to commit both
patches unless you think either is missing some must-have features. I
believe the consensus was that server version cache is not a must-have,
but please correct me if I am wrong.

Please see patch preamble for the proposed commit message with details.
I will just highlight one unsolved problem and one question here:

* XXX: If there is a chunks parsing error, the new code just resets the
connection. I tried to find a way to send an error page to the client,
but failed to do so. It is easy to do when the headers and the body
prefix is parsed, but if the error is send later, the server-side may
start sending us its response, and the two responses would clash,
causing assertions. I do not know how to fully avoid that. Search for
WE_KNOW_HOW_TO_SEND_ERRORS.

* We handle identity transfer encoding when accepting requests. HTTPbis
dropped identity transfer encoding from the specs. I do not know whether
some clients use it. Should we drop it too, responding with an error, as
we would for other unsupported encodings?

Thank you,

Alex.