Bug 15505: Mark Hold Items 'On hold' instead of 'Available'

Bug 15505: Mark Hold Items 'On hold' instead of 'Available'

This patch adds a 'pending hold' column to C4::Items:GetItemsInfo to
allow for displaying status of an item when it has been selected for a
hold by the holdsqueue and AllowItemsOnHoldCheckout is set to 'Don't
allow'

To test:
00 - Set AllowItemsOnHoldCheckout to 'Allow'
01 - Place a hold on an item
02 - Build the holdsqueue (kohadevbox example below)
      sudo koha-shell kohadev
      perl misc/cronjobs/holds/build_holds_queue.pl
03 - Search for the item on the OPAC
04 - Note item shows as 'Available' in results and details
05 - Toggle AllowItemsOnHOldCheckout to 'Don't allow'
06 - Repeat search, note there is no change
06 - Apply Patch
07 - Search for the item on the OPAC
08 - Note that item now shows as 'Pending hold'
09 - Toggle AllowItemsOnHoldCheckout to Allow
10 - Note item shows as available
11 - prove -v t/db_dependent/Items.t

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>