Added MSV1_0_ALLOW_MSVCHAPV2 flag to ntlm_auth

Added MSV1_0_ALLOW_MSVCHAPV2 flag to ntlm_auth

An implementation of https://lists.samba.org/archive/samba/2012-March/166497.html (which has been discussed in 2012, but was never implemented).

It has been tested on a Debian Jessie system with this patch added to the Debian package (which is currently 4.1.17). Even though this is Samba 4, the ntlm_auth installed is the one from Samba 3 (yes, it surprised me too). The backend was a machine with Windows 2012R2.

It was first tested with the local security policy 'Network Security: LAN Manager authentication level' setting changed to 'Send NTLMv2 Response Only' (allow ntlm v1). This way we are able to authenticate with and without the MSV1_0_ALLOW_MSVCHAPV2 flag (as expected).

After the basic step has been verified, the local security policy 'Network Security: LAN Manager authentication level' setting was changed to 'Send NTLMv2 Response Only. Refuse LM & NTLM' (only allow ntlm v2). The behaviour now changed according to the MSV1_0_ALLOW_MSVCHAPV2 flag (again: as expected).

  $ ntlm_auth --request-nt-key --username=XXXXXXXXXXXXX --challenge=XXXXXXXXXXXXXXXXX --nt-response=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --domain=
  Logon failure (0xc000006d)
  $ ntlm_auth --request-nt-key --username=XXXXXXXXXXXXX --challenge=XXXXXXXXXXXXXXXXX --nt-response=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --domain= --allow-mschapv2
  NT_KEY: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

The changes in `wbclient.h` are intended for programs that use libwinbind directly instead of authenticating via `ntlm_auth`. I intend to use that within FreeRADIUS (see https://bugzilla.samba.org/show_bug.cgi?id=11149).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11694
Signed-off-by: Herwin Weststrate <herwin@quarantainenet.nl>
Reviewed-by: Kai Blin <kai@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>