Partly revert cb7eb674accd24b6b73f26ef23cf4a301b6ebfaf

Fixes #13911
Update dependencies.
Turn off clean-css' advanced optimizations.

Works around #13914.

We might give it another go in the future but the stuff this breaks over the time does not justify having it enabled. The gain in size is negligible:

dist/css/bootstrap.min.css: 108.65 kB → 109.5 kB
dist/css/bootstrap-theme.min.css: 18.84 kB → 18.86 kB
docs/assets/css/docs.min.css: 20.44 kB → 20.61 kB
Run `grunt`.
Merge pull request #13913 from hnrch02/webkit-keyframes

Partly revert cb7eb674accd24b6b73f26ef23cf4a301b6ebfaf
Move variable declaration before its use for Sass

In Sass, variable must be declared before it is used.
This also removes Miscellaneous section, because horizontal line color
and form / list paddings are Typography.
upgrade grunt-saucelabs to ~8.1.0

update shrinkwrap too
retry each test up to 3 times in the event of timeout

Big thanks to @gvas for https://github.com/axemclion/grunt-saucelabs/pull/136 ! <3
Merge pull request #13916 from glebm/variable-order

Move variable declaration before its use (for Sass)
Merge pull request #13918 from twbs/sauce-with-retries

Enable retrying of timed-out Sauce tests
reenable OS X Chrome in Sauce
reenable Win7 IE8-9 in Sauce
Merge pull request #13781 from twbs/saucier

Reenable additional Sauce browsers
update shrinkwrap to get clean-css v2.2.3

Refs #13914
Refs https://github.com/GoalSmashers/clean-css/issues/302
Revert "Turn off clean-css' advanced optimizations."

This reverts commit 25ca51319b016bc4e42e1ba882d6f191e001d65d.
grunt dist; closes #13914
Revert "Revert "Turn off clean-css' advanced optimizations.""

This reverts commit e31c2edf885efd42d2e755f189cc15125d977d70.
Run `grunt`.

Revert a991cd572c8b3cafa6228915ca86f7a0cdd26e2d.