A `<label>`'s activation behavior shouldn't be platform specific

The first example of the label element contains:

"For example, on platforms where clicking a checkbox label checks the checkbox, clicking the label in the following snippet could trigger the user agent to fire a click event at the input element, as if the element itself had been triggered by the user:"

Tests on different platforms (Ubuntu, Windows, OSX) have shown the behavior there is the same. At least for Chrome and Firefox (although their behavior differs in at least one case, but is consistent across all platforms).

Instead, it seems the dispatch algorithm should account for changing the target to the labeled control, if existing. I'll file a separate issue for that at whatwg/dom and link it here.

Read the label element example in the HTML Standard and compare it with the linked DOM dispatch algorithm and labeled-control definition. Verify the reported cross-platform behavior, then determine whether the HTML wording or the DOM algorithm needs adjustment; done means the relevant specification text consistently describes the intended behavior and coordinates with the separate whatwg/dom issue.