Use a time constant in get_theme_feature_list() and File_Upload_Upgrader.

props GaVrA.
fixes #28124.
Built from https://develop.svn.wordpress.org/trunk@28253


git-svn-id: http://core.svn.wordpress.org/trunk@28081 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid displaying a negative number of plugin updates in admin menu.

fixes #28073.
Built from https://develop.svn.wordpress.org/trunk@28254


git-svn-id: http://core.svn.wordpress.org/trunk@28082 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix closing tag in image editor.

props t4k1s.
fixes #28130.
Built from https://develop.svn.wordpress.org/trunk@28255


git-svn-id: http://core.svn.wordpress.org/trunk@28083 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Deprecate unused argument of delete_plugins(). Clarify @return value.

props jdgrimes for initial patch.
fixes #28111.
Built from https://develop.svn.wordpress.org/trunk@28256


git-svn-id: http://core.svn.wordpress.org/trunk@28084 1a063a9b-81f0-0310-95a4-ce76da25c4cd