Fix for SearchModelAdmin under Django 1.5

Some of the boilerplate from Django's admin changelist view changed between 1.4 and 1.5.  This merges the Django change into the Haystack code.

Before the fix:
When searching on a SearchModelAdmin view, the checkboxes to the left of the items would not be visible and it would say "of XX selected" rather than "0 of XX selected".

After the fix:
View when searching via SearchModelAdmin, it now looks identical to the default Django ModelAdmin search view.