4.0 version bumps.

props kworthington.
fixes #27872, #27873.

Built from https://develop.svn.wordpress.org/trunk@28175


git-svn-id: http://core.svn.wordpress.org/trunk@28006 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove version string from Thickbox so it assumes the WP core version. Bust some caches.

props celloexpressions.
see #27861, for trunk.

Built from https://develop.svn.wordpress.org/trunk@28176


git-svn-id: http://core.svn.wordpress.org/trunk@28007 1a063a9b-81f0-0310-95a4-ce76da25c4cd