Bug 18987 - Added Koha::Account package pragma to Patron.pm

Bug 18987 - Added Koha::Account package pragma to Patron.pm

Test plan:
1. On an up to date branch go to Patrons and try to browse for a patron
by last name
2. Notice that the page processes indefinately
3. Apply patch
4. Repeat step 1
5. Notice the patron results are displayed

Signed-off-by: David Cook <dcook@prosentient.com.au>
Works as described.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>