Bug 31565: Escape datatables MySQL special characters only in LIKE queries

Bug 31565: Escape datatables MySQL special characters only in LIKE queries

Escaping \ yields no results when performing exact search in datatables.
This patch adds MySQL special character escaping only to LIKE searches.

To test:
1. Add following categorycode 'TEST\CAT' by SQL
insert into categories (categorycode,description) values ('TEST\\CAT', 'TEST\\CAT');
2. Add a patron into TEST\CAT category
3. Go to patron search
4. Limit search by category TEST\CAT
5. Observe no results
6. Apply patch
7. Refresh patron search page
8. Limit search by category TEST\CAT
9. Observe Koha redirecting you to patron you chose in step 2

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>