s4:dsdb/rootdse: Support netlogon request

s4:dsdb/rootdse: Support netlogon request

This patch adds support for a netlogon ldap style request
over the tcp socket.  This is available since win2k3+ [1].

The automatic client join & configuration daemon "realmd" makes
use of this ability.
Realmd can now be used to join a computer to a samba 4 domain.
(See also:
https://lists.samba.org/archive/samba-technical/2013-October/095606.html)

Tested with:
ldapsearch -h samba-srv -x -b '' -s base "(&(NtVer=\06\00\00\00)(AAC=\00\00\00\00))" NetLogon

And compared the result in wireshark with cldap request issued by
examples/misc/cldap.pl.

[1]: http://wiki.wireshark.org/MS-CLDAP?action=recall&rev=8

Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Nadezhda Ivanova <nivanova@symas.com>