Primary Group SID

[Bostjan Golob]

Attached is a patched patch that first checks if it can get the
gidNumber from LDAP. If not, it goes through getpwnam() to acquire the
primary gid number.

If primary GID->SID translation is too expensive for init_sam_from_ldap,
I can patch get_domain_user_groups from rpc_server/srv_util.c to do it
instead when enumerating the user's groups. It will require a getpwnam()
call though, and I don't know how much code checks the primary group SID
only.

Bostjan Golob