Bug 26328: Cast barcode from varchar to integer for incremental barcode

Bug 26328: Cast barcode from varchar to integer for incremental barcode

Without this patch, the incremental barcode generation will
treat 978e0143019375 as having an exponent and interpret it as a very
large number.

With this patch, the incremental barcode generation will first cast
barcode varchar strings to integers before finding a max() value.
In this case 978e0143019375 becomes 978 instead of
1.7976931348623157e308

Test plan:

0. Using koha-testing-docker

Before applying patch:

1. Go to http://localhost:8081/cgi-bin/koha/admin/preferences.pl?op=search&searchfield=autobarcode
2. Set to "generated in the form 1, 2, 3"
3. Go to http://localhost:8081/cgi-bin/koha/cataloguing/additem.pl?biblionumber=1#additema&searchid=scs_1607059974968
4. Add item with barcode 978e0143019375
5. Click "p - Barcode"
6. Note the barcode is "Inf"

After applying patch:
1. Go to http://localhost:8081/cgi-bin/koha/cataloguing/additem.pl?biblionumber=1#additema&searchid=scs_1607059974968
2. Click "p - Barcode"
3. Note the barcode is "39999000019194"

Signed-off-by: Marjorie <marjorie.barry-vila@collecto.ca>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>