Factor "identity" transfer encoding support out of HTTPChannel.rawDataReceived into an object like the chunked transfer encoding object

[exarkun]

This will simplify rawDataReceived and make the code re-usable by the HTTP client.

[exarkun]

(In [25869]) Branching to 'identity-transfer-encoding-3605'

[exarkun]

Please review.

The noMoreData methods may seem like a strange addition since there are no callers. However, the HTTP client will call this method. Since I developed this code in the client branch, I'd already written them and the tests. It seems like a waste of time to try to split up this code any more. Once the HTTP client code is merged, there will be callers.

[therve]

I just have one question: why making _DataLoss private and PotentialDataLoss public? Can you add a small comment in the source to explain that?

Otherwise, this is nice, please merge.

[exarkun]

(In [25946]) expand _DataLoss docstring

refs #3605

[exarkun]

(In [25947]) expand PotentialDataLoss docstring a bit

refs #3605

[exarkun]

(In [25948]) Merge identity-transfer-encoding-3605

Author: exarkun, itamar Reviewer: therve Fixes: #3605 Refs: #886

Add an identity transfer-encoding decoder, similar to the chunked transfer-encoding decoder, to twisted.web.http and use it to simplify HTTPChannel slightly by removing the knowledge of any particular transfer-encoding from its request body handling code.

Also expand the transfer-encoding decoder interface so that it will be useful for an HTTP client and rename the chunked decoder so that its name more closely reflects what it does.