* parser now has a callback feature for intercepting chunk headers
and chunk bodies
* The names for basic_parser derived class callbacks have been
refactored
* basic_parser offers an additional callback for distinguishing
chunk body data.
Actions Required:
* Adjust signatures for required members of user-defined
subclasses of basic_parser
* Use the new basic_parser chunk callbacks for accessing
chunk extensions and chunk bodies.
fix#185, fix#489
* SSE4.2 is detected
* basic_parser uses SSE4.2 if available
* basic_parser tries to parse on the initial buffer and if
it does not find the end of header it shifts to a new
strategy of waiting for the end of header to defeat
slow loris attacks. This coincidentally is also faster
than the previous algorithm.
`put` returns the number of bytes actually transferred
from the input buffers.
Actions Required:
* Return the number of bytes actually transferred from the
input buffers in user defined `Body::writer::put` functions.
Vinnie Falco