Eliminate the 1px padding adjustment on active buttons because it creates an...

Eliminate the 1px padding adjustment on active buttons because it creates an un-clickable dead zone 1px high and spanning the entire width of the button. Modify the background color of active buttons for better contrast to make the active state more obvious.

See #26700, props johnbillion.


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git-svn-id: https://core.svn.wordpress.org/trunk@26870 1a063a9b-81f0-0310-95a4-ce76da25c4cd