Design and implement new protocol in the new libdrizzle

See the libdrizzle project for details and status on this.

A proposed draft of the new protocol is given in the attached specification URL. To summarize, the protocol changes include:

* Length encoding mechanism has changed, there is no longer a 3-byte
  length option.

* Length encoded packet sizes. This is to reduce packet size and
  allow for much larger packets to be sent.

* Packet sequence number removed from packet header since this
  duplicates TCP functionality.

* Command identifier added to packet header to track concurrent command
  and result packets on a single connection.

* Attributes in packets are specified as variable keys and values
  rather than a predefined structure. This allows the protocol to
  stay flexible in the future.

* Pluggable authentication system.