drepl: Support GET_TGT on periodic replication client

drepl: Support GET_TGT on periodic replication client

- Update IDL comments to include Microsoft reference doc
- Add support for sending v10 GetNCChanges request (needed for the
  GET_TGT flag, which is in the new 'more_flags' field)
- Update to also set the GET_TGT flag in the same place we were setting
  GET_ANC (I split this logic out into a separate function).
- The state struct now needs to hold a 'more_flags' field as well (this
  flag is different to the GET_ANC replica flag)

Note that using the GET_TGT when replicating from a Windows DC could be
highly inefficient. Because Samba keeps the GET_TGT flag set throughout
the replication cycle, it will basically receive a repeated object from
Windows for every single linked attribute that it receives.

I believe Windows behaviour only expects the client to set the GET_TGT
flag when it actually needs to (i.e. when it receives a target object it
doesn't know about), rather than throughout the replication cycle.
However, this approach won't work with Samba-to-Samba replication,
because when the server receives the GET_TGT flag it restarts the
replication cycle from scratch. So if we only set the GET_TGT flag when
the client encountered an unknown target then Samba-to-Samba could
potentially get into an endless replication loop.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12972