Bug 13609: Cross Site Scripting problem in authority search result list paging

Bug 13609: Cross Site Scripting problem in authority search result list paging

To test:
- Use an installation a reasonable amount of authorities, so that you can
  have a search result list with more than one page
- Activate OpacAuthorities
- Create an OPAC link like shown below, verify that an alert is shown
- Apply patch
- Refresh the page and no alert should appear
- Verify the paging still works correctly for 'numbers' and 'arrows'

URL:
.../cgi-bin/koha/opac-authorities-home.pl?and_or=and&marclist=match&op=do_search&operator=contains&orderby=HeadingAsc2"><script>prompt(987898)</script>

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>