Bug 4276: XSLT subject tracings only use subfield a

Bug 4276: XSLT subject tracings only use subfield a

When XSLT is enabled, the subject tracings on the details view (both OPAC and
Intranet) previously only searched on the subfield 'a'. In addition, searches
failed when the tracing included parentheses, and the XSLT display did not
include subfields other than abcdvxyz, even for those 6xx tags that have other
subfields.

This patch adds a syspref: TraceSubjectSubdivisons. When
TraceSubjectSubdivisions is set to "Don't include" (default), the subject
tracings in the XSLT details view will only search on subfield 'a'. When
TraceSubjectSubdivisions is set to "Include", the subject tracings will search
on all subfields, not just subfield 'a'.

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>