Bug 19398: Format date of birth in circ patron search

Bug 19398: Format date of birth in circ patron search

When searching for a patron from the circulation tab, the results table
shows the date of birth unformatted.

Test plan:
Apply this patch, search for patrons in the circ tab and confirm that
the date of birth are correctly formatted according to the dateformat
syspref

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>