Undeleting bibs does not null merged_to column

[Blake GH]

EG 3.1

When merging bibs in 3.1, as per bug 1744996, two columns are populated with date and ID of the winning bib. In addition to that, the bibs that are being deleted also receive a null value for column vis_attr_vector.

When a previously-merged-bib is undeleted, the undeleted bib still retains the merged_to value and the merge_date value. This has some implications elsewhere in the codebase. Also, I'm not certain, but the SQL triggers should perform biblio.calculate_bib_visibility_attribute_set upon the undeleted bib as part of the undeleted process. It doesn't seem like it is doing that.

[Blake GH (bmagic)]

Also related:
bug 1091885

metabib.record_attr_vector_list needs regenerated.