Deprecate IntNStringReceiver.recvd

[therve]

It was kept for compatibility purpose when the latest optimization was introduced, it should be deprecated.

[therve]

(In [37980]) Branching to 'deprecated-recvd-5770'

[therve]

Ready for review, build results here: ​http://buildbot.twistedmatrix.com/boxes-supported?branch=/branches/deprecated-recvd-5770

[Glyph]

Thanks for fixing this.

Looks fine, modulo some minor points:

1. I think that ​these pyflakes errors are spurious, but if not, fix it.
2. clearBuffer's docstring really should be a lot better. What is "the current buffer"? It might be best to describe this in terms of the behavior of stringReceived and dataReceived.
3. # new protocol: luckily it's giving that with a handy method is not a very useful comment. Perhaps if clearBuffer's docstring explained what it did, this comment could simply be eliminated.

Please address to your satisfaction and merge.

[Jean-Paul Calderone]

Do we not care that clearing a buffer provides a smaller feature set than being able to assign to recvd? It might be nice to see a unit test that does the same thing as test_recvdChanged without using a deprecated API. And it seems like we're just discarding the feature of being able to inspect the current buffer?

[Jean-Paul Calderone]

Also, doesn't the set-case warning point to the wrong code? The test asks for deprecations pointed at test_recvdChanged, but that's not where the code that writes to recvd is.