Rename the old media.css file, used for the pre-3.5 media library. Clean up...

Rename the old media.css file, used for the pre-3.5 media library. Clean up script-loader CSS registrations.

see #26669.

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git-svn-id: https://core.svn.wordpress.org/trunk@27042 1a063a9b-81f0-0310-95a4-ce76da25c4cd