Shouldn't really happen, but China for example has blocked Google so this should help.

as role="menu" is a very specific (and strict) ARIA pattern for
desktop-like application menus, and our dropdowns are often used
as pure navigation dropdowns, this change abandons ARIA menus for
a more open-ended and light-weight approach
(see http://heydonworks.com/practical_aria_examples/#submenus and
http://www.w3.org/WAI/tutorials/menus/flyout/#improve-screen-reader-support-using-wai-aria)
note that in dropdown.js, switched to now target ``.dropdown-menu``
instead of ``role["menu"]`` - this also prevents bootstrap scripts
from "bleeding" into non-bootstrap components on the same page.
also removed the ``role=["listbox"]`` part, which appears to be
vestigial/unused (only place in bootstrap that uses that
role are carousels, and their key handling is done separately)

http://www.w3.org/TR/wai-aria/roles#separator

[ci skip]

And add explanatory comments to the Carousel & Dashboard examples regarding holder.js

[skip sauce]

The revert was incomplete.

Fix issue #15601 — Position of X-UA-Compatible, charset and viewport

Add comment to all examples

The non-responsive is correctly saying 2 instead of 3

When the screen is shrunk below the md threshold, all the featurette columns stack.
However, since the second featurette is "backwards", when stacked the second featurette
looked awkward as the image came before the heading.

In order to see the changes, you must shrink the browser to below the md threshold.

Use a simple blank.gif and change the background color instead of duplicating stuff.

plus one example that still used the old <div role="navigation"> and a
fix-up of the callout as per
https://github.com/twbs/bootstrap/issues/15109

adding explicit aria-expanded="false" initial state (so they're
correctly announced by AT as being collapsed), and - in the case of
old-school use of <a> - role="button"

plus minor tweak to customizer's generated alerts

[ci skip]

Added handling of aria-expanded=true/false to collapse.js, updated
documentation to include advice on making expand/collapse controls
accessible, updated examples and javascript documentation to use
aria-expanded and aria-controls (when targetting single collapsible
element, using ID rather than class selector)

Closes #14147.
Closes #14153.

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]

This way, it works in all browsers.

Docs audit prompted by #13697.
[skip sauce]

The validator doesn't choke anymore on this and even though it's not spec compliant, it's needed for some IE versions. So until we move favicon.ico in root, this should do the job.

Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

Closes #13379.

Also, use Google's CDN per #11369.

Replaces links to holder.js with links to the new docs.min.js.
The uncompressed holder.js file is now in docs/assets/js/vendor,
which is excluded from Jekyll builds. In turn, Holder is now
included in docs.min.js, which is smaller than holder.js,
so this should make everybody happy. :)