Bug 22749: Make Koha::Item->hidden_in_opac respect hidelostitems

Bug 22749: Make Koha::Item->hidden_in_opac respect hidelostitems

This patch makes Koha::Item->hidden_in_opac take hidelostitems into
account when performing the calculation.

To test:
- Apply the regression tests patch
- Run:
  $ kshell
 k$ prove t/db_dependent/Koha/Item.t
=> FAIL: Tests fail because the code doesn't (yet) care about the
syspref
- Apply this patch
- Run:
 k$ prove t/db_dependent/Koha/Item.t
=> SUCCESS: Tests pass!
- Sign off :-D

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>