Bug 12252: OAI-PMH items respect OpacHiddenItems

Bug 12252: OAI-PMH items respect OpacHiddenItems

This allows the OAI-PMH service to not provide item information when
there is a rule that would supress it in OpacHiddenItems.

Test plan:
* Find an OAI-PMH URL that shows you some items.
* Add an entry to OpacHiddenItems that would block that.
* Check that it's blocked.

Signed-off-by: Frederic Demians <f.demians@tamil.fr>

Tested, playing with OpacHiddenItems. GetRecord OAI verb returns a record
complying with OpacHiddenItems rules, for example without items from a specific
library.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>

Signed-off-by: Signed-off-by: Gaetan Boisson <gaetan.boisson@biblibre.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>