* HTTP read and write operations now return the
number of bytes transferred to or from the stream.
Actions Required:
* Modify HTTP read and/or write completion handlers to receive
the extra std::size_t bytes_transferred parameter.
fix#692
The value of Content-Length is not checked for limits
when the semantics of an HTTP response indicate that
the message has no body. For example, when status is 101.
Vinnie Falco