Fix struct loststr / struct empobj mismatch corrupting lostitems

Fix struct loststr / struct empobj mismatch corrupting lostitems

The initial parts of struct loststr and struct empobj must match.
Commit 49780e2c screwed that up for members lost_uid/uid, which also
broke the equivalence of lost_owner/own.  Since lost_uid is not used,
the former had no effect.  But the latter broke xdvisible().  Could
make xdump lost leak information.

Commit a680c811 reorderd struct loststr members to make lost_timestamp
equivalent to new struct empobj member timestamp, but failed due to
the bug in commit 49780e2c.  Commit f33b96b1 then set the timestamp
through empobj, which screwed up timestamps in lostitems, i.e. it
broke incremental xdump lost.

All of the above is in v4.3.12.

Commit 536ef0b0 (v4.3.15) added lost_seqno / seqno.  No effect,
because only seqno is used.
(cherry picked from commit eb252201b69a591523e8a68b41c01f4a80e7b731)