Update affix properly on scrollspy speedy scroll to top of page #11310

Fix scrollspy.js so as affix is updated properly when user scrolls fast
to top of page.

A fix for issue #11310.
Allow listbox AIRA role on dropdown component.
Merge two fs variable declarations into one

One is enough.
fixes #11288 - Vertical scroll position of modal saves between openings
Merge branch 'master' of github.com:twbs/bootstrap
Merge branch 'scrollspy-speedy-scroll-top' of git://github.com/ziogaschr/bootstrap into ziogaschr-scrollspy-speedy-scroll-top

Conflicts:
	dist/js/bootstrap.min.js
fixes #11373 - adds related target to dropdown events
fixes #11379 - Fix carousel this.sliding not getting reset if $next.hasClass('active')
Merge branch 'dropdown-aria-roles' of git://github.com/plumlee/bootstrap into plumlee-dropdown-aria-roles

Conflicts:
	js/dropdown.js
Merge pull request #12036 from ZDroid/grunt-fs-minify

Merge two fs variable declarations into one
Merge branch 'master' of github.com:twbs/bootstrap
add note about ios dropdown compat