Bug 7421: add regression tests for UNIMARC authorities DOM indexing

Bug 7421: add regression tests for UNIMARC authorities DOM indexing

This patch enhances  t/db_dependent/Search.t to test indexing and
searching of authority records.  It supplies a sample authority file
for MARC21 (consisting of the record for William Shakespeare from the
Library of Congress) and a sample UNIMARC authority file supplied
by Henri-Damien Laurent.

It also adds tests for both MARC21 and UNIMARC authorities.

When the main patch for bug 7421 is applied, t/db_dependent/Search.t
should pass.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>