Attempt to fix one of the last two bugs with the full Windows ACL support.

When returning an underlying ACL on a directory, normally on a
POSIX system it has no inheritable entries, which breaks the
Windows ACL when a user does a get/set of a Windows ACL on a
POSIX directory with no existing stored Windows ACL from
the Windows ACL editor. What happens is any new entry added
by the user gets set inheritable, but none of the others
entries are (as returned by default). So any new files then
only inherit the single new ACE entry (the one marked inheritable
by the ACL editor).

Fix this by faking up a default 3 element inheritable ACL that
represents what a user creating a POSIX file or directory will
get by default from the smbd code.

Jeremy.