NT systems, read primary group SID from process token. Use that info
to create correct group entry. On error or on 9x systems fallback
to emulating Administrators group as before.
(read_etc_passwd): When emulating nonexisting passwd file on NT systems,
read user and primary group SID from process token. Use that info to
create correct passwd entry. On error or on 9x systems fallback to
emulating user with Administrator user id and Administrators group
as before.
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