Bug 19616: (follow-up) Breaking items according to punctuation

Bug 19616: (follow-up) Breaking items according to punctuation

Previously the code assumed that $t indicates a new line in the
listing. But this is not true. The standard tells us that -- or
.-- will indicate a new item.

"In records formulated according to AACR 2, a space-hyphen-hyphen-space
( -- ) is recorded between each item in the contents note unless a
delimiter/subfield code follows in which case there is no ending space.
In pre-AACR 2 records, items are separated by a period-hyphen-hyphen (.--)."

The previous logic did no longer work with $g added. From the LOC
examples:

This would work:
505 2 0 $tBaptisms, 1816-1872 --$tChurch members, 1816-1831 --$tHistory of the Second Presbyterian Church of West Durham /$rby L. H. Fellows.
505 0 0 $tQuatrain II$g(16:35) --$tWater ways$g(1:57) --$tWaves$g(10:49).

This wouldn't:
505 1 0 $gNr. 1.$tRegion Neusiedlersee --$gNr. 2.$tRegion Rosalia/Lithagebirge --$gNr. 3.$tRegion Mettelburgenland --$gNr. 4.$tRegion südliches Burgenland --$gNr. 5.$tRegion Südburgland

With the patches applied, all examples should display nicely now.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>