This check is in place in most other places, mostly because we have
run into widespread issues under similar circumstances and we like to
avoid those, but it was forgotten here. There also were no tests
covering this, so it was never caught.

This adds tests that ensure that the option in the results list will
be generated with the correct "disabled" state based on whether or
not it, or a parent element, is marked as disabled.

This should have been easy: just check element.disabled

Unfortunately the disabled property is not inherited within the
option chain, so if an <optgroup> is disabled, the <option>
elements or other <optgroup> elements held within it do not have
their disabled property set to true. As a result, we needed to
use the matches method to check if the :disabled state is
present for the element. The matches method is part of the official
standard, but it was not implemented under that name for a while and
as a result Internet Explorer only supports it under the prefixed
msMatchesSelector method and older versions of Webkit have it
implemented as webkitMatchesSelector. But once we use this method,
it appears to consistently return the expected results.

This matches method and prefixed predecessors are not supported in
IE 8, but they are supported in IE 9 and any browsers newer than
that. Instead of buulding a very hacky solution using
querySelectorAll that was brittle, I have chosen to act like
everyone else and pretend IE 8 no longer exists.

Fixes #3347
Closes #4818

This pull request includes a

• Bug fix
• New feature
• Translation

The following changes were made

• Added tests for the disabled property on options
• Options in results now check the disabled behaviour on options in <select> elements