Bug 9988: Table revision for need_merge_authorities

Bug 9988: Table revision for need_merge_authorities

In order to let merge do exactly the same when called from the merge
cron job, we need three additional fields in the table. The use of these
fields will be explained in a follow-up.

Test plan:
Run the dbrev (updatestructure step in webinstaller).

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Also tested running kohastructure.sql for this table.

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jacek Ablewicz <abl@biblos.pk.edu.pl>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>