empdump: Omit redundant data from export, new -c includes it

empdump: Omit redundant data from export, new -c includes it

Cuts size of export files in test suite by a factor of four.  Not a
big deal for disk usage, as export files compress very well, and disk
space is cheap anyway.  Export files are simply easier to work with
when they aren't full of redundant crap.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>