Theme Installer: Fixes for browsers without pushState.

props gcorne.
see #27055.

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TinyMCE: fix icons in IE7, fixes #27829
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Widgets: Remove create_function() from the customizer class.

props westonruter.
fixes #27805.

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Graceful failures for TinyMCE views of video/audio playlists.

props gcorne.
fixes #27821.

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Translate a string added in 3.7.1 but never translated previously.

props SergeyBiryukov.
fixes #27819.

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About page: Use a better preposition to describe drag-and-drop.

see #27713.

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