Fixes #14038.

Research supporting this choice of approach:
    https://gist.github.com/cvrebert/68659d0333a578d75372

Why not <button>?
Even with a `tabindex` attribute, they don't gain focus when clicked upon in:
    * Mac OS X Firefox 30.0
    * Mac OS X Safari 7.0.5

Fixes #14095: Add basic styling for captions, which we've for some reason been missing all this time.

Fixes #12738 again: use max-device-width instead of max-width for .navbar-collapse height in landscape devices

[skip sauce] [skip validator]

[skip sauce]

.bs-docs-navbar class doesn't seem to be used anywhere at all

Revert a991cd57.

Will hopefully revert this reversion and land a fully-working version of UMD in v3.3.0.

Revert "some changes from #13801 - add strict mode back and =="
This reverts commit 2b302f69.

Revert "Fix regression of #10038 introduced by #13772"
This reverts commit e9d6756a.

Revert "MD/CommonJS/Globals #12909"
This reverts commit 1c6fa901.

Revert "address #13811"
This reverts commit f347d7d9.

Conflicts:
    js/carousel.js
    js/collapse.js
    js/dropdown.js
    js/modal.js
    js/tab.js
    js/tooltip.js