fs/p9p/new: stat implementation and correct dir/Rstat encoding Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: refactor channel framing After a few connection bugs and framing issues, the transport has been refactored into a channel that manages raw message sending. More importantly, this frees up pre-session protocol version negotiation. To support this, the encoder and decoder have been folded into a Codec interface. The encoding support still needs work, but this has made the server and client code much simpler to understand. 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: 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>

Both filesystem interfaces in master (fs & fs_tmp)