Plugin install: Remove columns and screen options.

fixes #28803.
Built from https://develop.svn.wordpress.org/trunk@29498


git-svn-id: http://core.svn.wordpress.org/trunk@29276 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Autoprefixer for [29496].

see #28844.
Built from https://develop.svn.wordpress.org/trunk@29499


git-svn-id: http://core.svn.wordpress.org/trunk@29277 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media: Apply attachment opacity only in grid mode.

see #28842.
Built from https://develop.svn.wordpress.org/trunk@29500


git-svn-id: http://core.svn.wordpress.org/trunk@29278 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Allow WebKit browsers to break strings in `<code>` tags.
This prevents an overflow for example on Permalink Settings.

fixes #28161.
Built from https://develop.svn.wordpress.org/trunk@29501


git-svn-id: http://core.svn.wordpress.org/trunk@29279 1a063a9b-81f0-0310-95a4-ce76da25c4cd