Enable persistent handles and continuous availability

[Christopher R. Hertel]

So...

I have thrown some code up on GitLab.  It's there until I manage to set up a
repository on samba.org under my name.  In the mean time:

  git at gitlab.com:crh/Samba_Persistent_Handles.git

or, just to take a look:


https://gitlab.com/crh/Samba_Persistent_Handles/commits/crh/continuousavailability

The important bits are:
  + Two XML files that provide the descriptions of the new parameters.
  + Default values for the new parameters, set in the appropriate places.
  + One additional field in the connection_struct to indicate whether or not
    continuous availability is active (has been announced) on a given tree
    connect.
  + Changes to smb2_negprot.c and smb2_tcon.c to enforce the rules and set
    the capability bits in the outgoing messages.

I have, of course, tested these changes and they don't seem to introduce any
new or strange problems.

Chris -)-----