Bug 21260: Create three main XSLT Availability segments

Bug 21260: Create three main XSLT Availability segments

XSLT changes:
[1] Add an item count at the start. Also add variables for counting
    status available and reference. Use these vars in the corresponding
    'blocks'.
[2] Refine the No items-test with the new itemcount.
[3] Combine the reallynotforloan block with the other statuses by
    refining (extending) its initial test. All if's are moved up into
    the former block but are unchanged.

Result of these changes makes that the Availability line consists of three
segments: 1 Available items, 2 Reference items, 3 Other statuses.

Test plan:
[1] Check a biblio without any items in the OAPC results. You should
    see the No items only here.
[2] Check a biblio with one item checked out. You should see only the
    'third' segment with Checked out(1).
[3] Check a biblio with one available and a notforloan==1. You should
    see segment 1 and 2. Both listing item call numbers.
[4] Check a biblio with one available and a notforloan==-1. You should
    see segment 1 and 3. Both listing item call numbers. (See also the
    following patch.)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: ava li <rubyli208@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>