Enable Class::DBI::Frozen::301 use for offline transaction management

Enable Class::DBI::Frozen::301 use for offline transaction management

Most modern systems will install Class::DBI::Frozen::301 to avoid
conflicts with incompatible Class::DBI packages. We need to teach
offline.pl how to use Class::DBI::Frozen::301 if it is available.

Note that we're using "use parent" instead of "use base" per the
recommendation of "perldoc base"; accordingly, we're adding the
system prerequisite for the parent pragma.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@17575 dcc99617-32d9-48b4-a31d-7c20da2025e4