Bug 14655: Add a warning on the about page if patrons have requested privacy

Bug 14655: Add a warning on the about page if patrons have requested privacy

New warning on the about page if at least a patron has requested a
privacy on checkin but the AnonymousPatron is not set to a valid patron.

Works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>
(cherry picked from commit aaf2903cc0e86a2e59b3c7e223d7d8a85778ca0d)
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Conflicts:
	about.pl