Enable marc2sre.pl to run reasonably fast with a large set of bibs

Enable marc2sre.pl to run reasonably fast with a large set of bibs

Our previous iteration of marc2sre.pl used an ILIKE stanza
beginning with a wildcard to match system control numbers
without having to specify the institution's MARC code.
This worked, but was painfully slow in large bib sets as
the database needed to use a bitmap index scan to find matches.

By adding a --prefix flag, the user can specify the institutional
MARC code for the set of records and we can use an exact match
against metabib.full_rec.value, which is immeasurably faster.
This is, of course, a problem if there are multiple institutional
MARC codes in use for a given set of bibliographic records.

git-svn-id: svn://svn.open-ils.org/ILS/branches/rel_2_1@20013 dcc99617-32d9-48b4-a31d-7c20da2025e4