This copies the `title` attribute of `<option>` and `<optgroup>`
tags to the `title` attribute of the options within the results
list and the selection when it is rendered.
For single selections, the `text` property on the data objects will
be used if the `title` attribute is not present, which will allow
for long names to still be viewable if they overflow the selection
container.
This also fixes a potential issue in browsers that did not support
the non-standard `innerText` property on DOM nodes. As the
`textContent` property is the standard, and it is supported on
IE 9+, we try to set that before falling back to `innerText`.
This closes https://github.com/select2/select2/issues/2530.
This closes https://github.com/select2/select2/pull/2889.
c2326209c2