MemBuf implements Packable interface

... detatch it from Packer wrapper class

diff --cc src/HttpMsg.cc
Simple merge

diff --cc src/HttpReply.cc
Simple merge

diff --cc src/adaptation/ecap/MessageRep.cc
Simple merge

diff --cc src/adaptation/icap/ModXact.cc
Simple merge

diff --cc src/client_side.cc
Simple merge

diff --cc src/errorpage.cc
Simple merge

diff --cc src/http.cc
Simple merge

diff --cc src/tunnel.cc
Simple merge