winbind: Add a GetNssInfo parent/child call

winbind: Add a GetNssInfo parent/child call

This call will be done in the idmap child. It is not 100% the right place,
but there is no better one available to me. It will become a replacement
for the "winbind nss info" parameter: This global parameter is good
for just one domain. It might be possible to have idmap backend AD for
different domains, and the NSS info like primary gid, homedir and shell
might be done with different policies per domain. As we already have a
domain-specific idmap configuration, doing the NSS info configuration
there also is the closest way to do it.

The alternative, if we did not want to put this call into the idmap child
would be to establish an equivalent engine like the whole "idmap config
*" just for the nss info. But as I believe this is closely related,
I'll just keep it in the idmap child.

This also extends the wbint_userinfo structure with pretty much all user
related fields. The idea is that the GetNssInfo call can do whatever it
wants with it.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>