Revisions UI: Increase the text contrast/color for the diffs. see #23810.

git-svn-id: https://core.svn.wordpress.org/trunk@23995 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Compress scripts/styles: 3.6-beta1-23995.

git-svn-id: https://core.svn.wordpress.org/trunk@23996 1a063a9b-81f0-0310-95a4-ce76da25c4cd