fs/p9p/new: working client to server communication A rather large commit, this provides the first working version of running the wire protocol over a connection. It is fairly shaky but we can already get portions of the repl emitting and receiving 9p messages. Other additions include the separate of client and transport. We've also made some adjustments to message instantiation. Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: add server stubs and various implementation notes Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: add several new message types for encoding Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: Add message definitions and support Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: Lock down encode/decode for 9p Among other things, this adds support for 9p encoding and decoding. We now have fully reflective message marshaling and unmarshaling. Other aspects of this commit include the code actually compiling and movement towards a testable interface. Signed-off-by: Stephen J Day <stephen.day@docker.com>