Prevent breadcrumb separator from getting underlined on hover when not using <ol> markup

[cvrebert]

Uses wacky IE hack explained in the answers to http://stackoverflow.com/questions/8820286/how-to-remove-only-underline-from-abefore
Fixes #18733.
Closes #18740.

[cvrebert]

Getting some obvious questions out of the way:

(1) No, the IE hack cannot be simplified to:

.breadcrumb-item:hover::before {
  text-decoration: underline;
  text-decoration: none;
}

It must be 2 separate rules.

(2) Yes, the IE hack does survive minification unscathed.

[cvrebert]

CC: @mdo @patrickhlauke for review

[mdo]

Hmm, how was this not a problem in v3? Wonder if it's a problem of using floats as well?

[cvrebert]

@mdo Because v3 required using <ol> markup for breadcrumbs. v4 lets you use a plain <div>; and indeed, the bug doesn't occur in v4 when using an <ol>.

[cvrebert]

@mdo Any further feedback?

[mdo]

Taking a look at a few ideas this weekend.

[mdo]

Ah, shit, I understand what's going on now. It's because the ::before is within the .breadcrumb-item, not actually before it. Rough.