LP#1526858: speed up queries for shelf-expired holds during checkin

LP#1526858: speed up queries for shelf-expired holds during checkin

This patch adds indexes on action.hold_request and tweaks
the definition of the alhr IDL view to more efficiently
identify holds that can be canceled if the "Clear Holds Shelf"
checkin modifier is in use.  This can prevent a problem
where such checkins can time out in very large databases.

The tweaks were created by Jason Etheridge and have been in
production at a large consortium for some time.

To test
-------
[1] With a suitably large database, set up an item that
    is on the holds shelf but has passed its shelf-expiration
    time, then check it in using the "Clear Holds Shelf" modifier.
[2] The checkin may fail with a "network failure" message due
    the query on the alhr timing out.
[3] Apply the patch and repeat step 1. This time, the checkin
    should succeed.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>