[skip sauce]
[skip validator]

Center .icon-prev and .icon-next the same way .glyphicon icon are.
And this is the html markup:
<a class="left carousel-control" href="#carousel-main-menu" role="button" data-slide="prev">
<span class="icon-prev" aria-hidden="true"></span>
</a>

This reverts commit b10b373c.

Resolves #14937.

Flagged upstream in bootstrap-sass by scss-lint

carousel.less has two typos in glyphicon classnames. fixed them.

Fixes #10903 and #10457: IE8-9 don't support events on elements without background-color, so we have to hack it

fixes #10115: Default carousel controls and Glyphicon controls should behave the same on small devices and up

The left control should be positioned from the left, while the right
control should be positioning from the right. Positioning both from the
left results in the right carousel control being incorrectly positioned
(most noticeable with a larger than normal font size).

Moved alerts, badges, button groups, buttons, carousel, close to
variables.less and customize.html

* Remove `@carousel-control-hover-color` since that's just the same as
the default control color and all we change is `opacity` (it's required
for specificity).
* Add vars to customizer
* Update customizer nav to include new section
* Remove the `li` from the var names
* Consolidate and simplify `text-shadow` vars

moved buttons.less, carousel.less & close.less in this commit

* No longer hidden by default--up to users to figure that part out with
longer content
* Cleaned up styles and spacing

Used laquo/raquo for control buttons
Updated docs