Make dotu setting per-connection - Server's dotu variable says wether dotu is supported or not. - Server's Marshaller moved into Sock.   - helper functions make calling the marshaller easy. - A Sock's Marshaller's dotu setting is downgraded to false if   negotiation of .u features fail. - Dir's marshalling function now takes a marshaller as an arg,   and receives one from the Sock object for the request being filled. - Minor client tweaks to accomodate changes in Sock.  In particular,   Client's marshaller goes away and uses the one that gets passed   in on the Sock.
Make dotu setting per-connection
- Server's dotu variable says wether dotu is supported or not.
- Server's Marshaller moved into Sock.
  - helper functions make calling the marshaller easy.
- A Sock's Marshaller's dotu setting is downgraded to false if
  negotiation of .u features fail.
- Dir's marshalling function now takes a marshaller as an arg,
  and receives one from the Sock object for the request being filled.
- Minor client tweaks to accomodate changes in Sock.  In particular,
  Client's marshaller goes away and uses the one that gets passed
  in on the Sock.

wca/py9p.u