r1521: Updates to our SMB signing code.

r1521: Updates to our SMB signing code.

- This causes our client and server code to use the same core code,
  with the same debugs etc.
- In turn, this will allow the 'mandetory/fallback' signing algorithms
  to be shared, and only written once.

Updates to the SPNEGO code
- Don't wrap an empty token to the server, if we are actually already finished.

Andrew Bartlett