Bug 30648: Record deleted_biblionumber in holds

Bug 30648: Record deleted_biblionumber in holds

This patch ensures the deleted biblionumber is recorded in current and previous holds
before the record is deleted

To test:
1 - Place and fill a few holds on a biblio, completing checkout to patron
2 - Place a few holds on the biblio and do not fulfill them
3 - Delete the items from the biblio via the DB (otherwise you cannot delete last item when there are holds)
    DELETE FROM items WHERE biblionumber={biblionumber}
4 - Delete the biblio
5 - Check the DB and confirm the deleted_biblionumber column has been filled
    SELECT reserve_id,deleted_biblionumber,biblionumber FROM old_reserves WHERE deleted_biblionumber = {biblionumber};
6 - Sign off!

Signed-off-by: Anneli Österman <anneli.osterman@koha-suomi.fi>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>