[libflow] dead code cleanup
Merge commit '72b9461fcc19cb771334585fd4ab66ddf4ae5f1c'
[libbase] dropped ConstBuffer (as BufferRef provides everything it was used for)
[libxzero] adapted to changes wrt ConstBuffer
[libxzero] HttpConnection: eliminate the need of knowing the listening socket.
[libxzero] HttpMessageParser: drops unneeded feature
Merge commit '6f1367594ae3113850b2a77c731c7e29cb1af6fe'
Merge commit '8ebd14e457652c2742ad4a12731de363b957c4fe'