Bug 9747: Fix NSB/NSE sorting issues on z3950 search results

Bug 9747: Fix NSB/NSE sorting issues on z3950 search results

At least the BNF server returns results containing non-sorting
characters (NSB/NSE).
In order to sort results according these characters, this patch adds a
new Datatable function.

Test plan:
- search 'tintin' on the z3950 search (cataloguing/z3950_search.pl)
- sort on title (default sort) and check that results are not well
  sorted.
- apply this patch
- do the same search and check that the first result is "Hergé. Les
  Aventures de Tintin..."
  The value of the cell is:
      <td>\88Hergé. Les \89Aventures de Tintin...</td>

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Works as advertised and doesn't break existing searching

Signed-off-by: Galen Charlton <gmc@esilibrary.com>