Categories not supported on hierarchical post types

[scribu]

After registering a post type like so:

	register_post_type( 'example', array( 
		'label' => 'Examples', 
		'hierarchical' => true,
		'taxonomies' => array('category')
	) );

1. Create a post in that post type and assign it a category.

2. Go to wp-admin/edit.php?post_type=example

3. The Categories column is present, but it's blank.

Per IRC discussion, it would make sense to merge display_page_row() with _post_row().

(In [15500]) In WP_Posts_Table, merge _single_row_hierarchical() and _single_row(). Fixes #14089; see #14579