Pointers for 3.9

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As discussed during the dev chat on Wednesday, we could benefit from some "pointing" to features in 3.9.

The big one is the widget customizer. Secondarily, Paste from Word could benefit from some help. While we could potentially do something for drag-and-drop or image scaling/editing, I'm not sold on those.

"Paste from Word" won't be a pointer (where would you point and when?), but rather an extra line of text in the "Paste from Text" dialog.

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The widgets pointer will show up when:

• On the widgets screen, pointing at the admin menu, when the admin menu is not collapsed.
• On the themes screen, pointing at the customize button.

It won't show in one location if they already dismissed it in the other location.

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In 28090:

Add a feature pointer for widgets in the customizer in 3.9. Remove older pointers from 3.3 and 3.4.

see #27777.

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In 28091:

Add an explanation for 'Paste from Word' in the 'Paste from Text' dialog.

fixes #27777. see #27160.

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In 28093:

The widgets pointer requires the edit_theme_options capability.

(It's hypothetically possible to have only switch_themes.)

see #27777.