Fix E_STRICT notice in wp_get_popular_importers(). see #24356.

git-svn-id: http://core.svn.wordpress.org/trunk@24378 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix E_STRICT notice in WP_MS_Themes_List_Table::single_row(). fixes #24356.

git-svn-id: http://core.svn.wordpress.org/trunk@24379 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove unnecessary esc_attr() call and redundant title attributes. props zeo. fixes #24437.

git-svn-id: http://core.svn.wordpress.org/trunk@24380 1a063a9b-81f0-0310-95a4-ce76da25c4cd