Added MSV1_0_ALLOW_MSVCHAPV2 flag to ntlm_auth

[github at samba.org]

New comment by qnet-herwin on Samba Github repository

https://github.com/samba-team/samba/pull/45#issuecomment-172519882
Comment:
Regarding the coupling between FreeRADIUS and Samba (as @mcnewton mentioned): Yes, it is preferable to use libwbclient directly, but I would still very much like to have WBC_MSV1_0_ALLOW_MSVCHAPV2 exported and get rid of these lines: https://github.com/FreeRADIUS/freeradius-server/blob/v3.0.x/src/modules/rlm_mschap/auth_wbclient.h#L10-L13