Bug 5868: Subject indexes do not search 6xx fields

Bug 5868: Subject indexes do not search 6xx fields

Prior to this change, the named Zebra Subject phrase index did not include the
600, 610, 611, 630, 654, 655, 656, and 657 fields. This could be seen in
searches such as: "su:Bible and su:N.T. and su:Matthew and su:Textbooks", which
should return a result with the following field:
=630  00$aBible.$pN.T.$pMatthew$vTextbooks.
This did not formerly work.

This patch modifies etc/zebradb/marc_defs/marc21/biblios/records.abs. This file
must be installed and biblios reindexed in Zebra for the changes made here to
affect records already in the catalog.

Signed-off-by: Stéphane Delaune <stephane.delaune@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>