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

We now detect a MsvAvTimestamp in target info as indication
of the server to support NTLMSSP_MIC in the AUTH_MESSAGE.

If the client uses NTLMv2 we provide
NTLMSSP_AVFLAG_MIC_IN_AUTHENTICATE_MESSAGE and valid MIC.

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>
