Correct `@since` tag in `count_user_posts()` docs.

Props pavelevap, DrewAPicture.
See #21364.
Built from https://develop.svn.wordpress.org/trunk@30328


git-svn-id: http://core.svn.wordpress.org/trunk@30327 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer: Improve ability to filter active state for widget area Customizer sections.

* Mark panels, sections, controls as active if preview explicitly indicates.
* Introduce `WP_Customize_Sidebar_Section` PHP class, and `SidebarSection` JS class.
* Move logic for determining whether a sidebar section is active from the `SidebarControl` to `SidebarSection`.

props westonruter.
fixes #30235.
Built from https://develop.svn.wordpress.org/trunk@30329


git-svn-id: http://core.svn.wordpress.org/trunk@30328 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Color Picker: Allow to override `mode` and `width` values for Iris via wpColorPicker options.

props jtsternberg.
fixes #30182.
Built from https://develop.svn.wordpress.org/trunk@30330


git-svn-id: http://core.svn.wordpress.org/trunk@30329 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: Add a transparent border to a link in the footer to avoid jumpiness on hover.

props iamtakashi.
fixes #30332.
Built from https://develop.svn.wordpress.org/trunk@30331


git-svn-id: http://core.svn.wordpress.org/trunk@30330 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix selector for the "Live Widget Previews" feature pointer.

props rzen.
fixes #30158.
Built from https://develop.svn.wordpress.org/trunk@30332


git-svn-id: http://core.svn.wordpress.org/trunk@30331 1a063a9b-81f0-0310-95a4-ce76da25c4cd