Remove theme support for 'menus' in unregister_nav_menu() when there are no more menus.

props kovshenin.
fixes #26900.

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Use filtered per_page value in WP_Plugin_Install_List_Table and WP_Theme_Install_List_Table.

props brasofilo.
fixes #25675.
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Convert docs for `wp_nav_menu()` arguments to a hash notation.

Fixes #27163.

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git-svn-id: http://core.svn.wordpress.org/trunk@27079 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix reversed return logic in the `wp_nav_menu()` phpdoc.

See #27163.

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Remove unused code from WP_Widget::update_callback().

props OriginalEXE.
fixes #24733.
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