MP6: Admin pointers on smaller screens

[johnbillion]

On smaller screens (ie. smartphones in any orientation, and tablets in portrait) some of the admin pointers are a hindrance more than a help.

Here's my quick review of our current admin pointers when viewed on a Nexus 4 Android phone:

• Admin Toolbar: Acceptable. Nicely centred.
• New Media Manager: Ok but not great. Passable I suppose.
• Compare Revisions: Broken. The arrow on the pointer is missing and covers up the item it's pointing at.
• Theme Customizer: N/A due to WIP changes to the Themes screen.

Additionally, on all admin pointers the 'Dismiss' link is a little small. We should bump up its font size a bit in narrower media queries.

Should we not show admin pointers for screen sizes below a certain size?

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Note: To get admin pointers to show up you'll need to remove the dismissed_wp_pointers user meta field for your user and roll back the initial_db_version site option (I just set mine to 1).

[iammattthomas]

A viewport width of 782px, when the sidebar menu gets hidden and most of our responsive layout adjustments kick in, seems to be the point at which pointers are no longer currently useful. I think it makes sense to hide them for now, but it would be helpful to actually make wp-pointer work at responsive sizes.

[iammattthomas]

In 26419:

Admin pointers don't work at responsive sizes because of responsive layout adjustments. Hide the pointers for now until they're made responsive. Fixes #25984.