CVE-2016-2110: auth/ntlmssp: implement new_spnego support including MIC checking...

CVE-2016-2110: auth/ntlmssp: implement new_spnego support including MIC checking (as server)

We now include a MsvAvTimestamp in our target info as indication
for the client to include a NTLMSSP_MIC in the AUTH_MESSAGE.
If the client uses NTLMv2 we check NTLMSSP_AVFLAG_MIC_IN_AUTHENTICATE_MESSAGE
and require a valid MIC.

This is still disabled if the "map to guest" feature is used.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11644

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>