Fix hover-tooltip flickering when mouse re-enters

- is(':visible') seems to be the only reliable check, without a refactoring of how hoverState is used
- tests need improvement
add entry for #14528 to Wall of Browser Bugs
Merge pull request #14531 from twbs/doc-14528

add entry for #14528 to Wall of Browser Bugs
Replace nonexistent .col-6 classes in offcanvas example with .col-xs-6

Fixes #14500
Merge branch 'thr3-arendt/patch-1'
Fixes #14437: Round the corners of table rows in panels as well as the cells
Fixed typos involving apostrophes

Added apostrophes to 3 words to indicate possession (i.e. ownership of something) instead of plurality (i.e. multiples of something).
Merge pull request #14535 from gitname/patch-1

Fixed typos involving apostrophes
Add section to docs explaining our stance on validators
Address #14541 by tweaking badge docs

* move unrelated .btn-primary example out of the pills subsection
* remove excessive .nav-stacked example
Merge pull request #14543 from twbs/validation-docs

Add section to docs explaining our stance on validators
Merge pull request #14546 from twbs/address-14541

Address #14541 by tweaking badge docs
Fixes #14545: Avoid strange formatting on vendor prefixing for placeholder
Merge pull request #14273 from sgonyea/master

Fix hover-popover/tooltip flickering when mouse re-enters
Merge branch 'master' of https://github.com/twbs/bootstrap

Conflicts:
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
Merge branch 'master' of https://github.com/renebentes/bootstrap

Conflicts:
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css