Inconsistency between disabled anchors

Created by: howardcox

Hi, I've noticed and was wondering whether there was a conscious decisions for:

a.btn.disabled having pointer-events: none;

https://getbootstrap.com/docs/4.1/components/buttons/#disabled-state

But anchors inside a Menu Item / split-button do not, and still have a pointer.

https://getbootstrap.com/docs/4.1/components/dropdowns/#disabled

I've also noticed that if we remove the href from an anchor (which makes the browser treat the anchor as non-interactable), the disabled style is actually overridden by:

a:not([href]):not([tabindex]) {
    color: inherit;
    text-decoration: none;
}

That's quite annoying.

I'd be happy to submit a PR to change both of these, if they weren't intentional decisions, otherwise I'll just override locally.

Examples:

http://jsfiddle.net/wxv3kbLm/