many_to_one filter can cause out of memory errors in views admin ui

content_hander_filter_many_to_one does not override admin_summary().

admin_summary() calls get_value_options(), and if you have a lot of nodes or users that can potentially be referenced, it will load all of them to try to put them in the summary - doesn't matter if the widget for the exposed filter is autocomplete or anything like that.

Wasn't 100% sure the best approach to take for this, I ended up adding a new handler, then setting both nodereference and userreference to use that.