jQuery positional selectors () have been deprecated in
[jQuery 3.4.0](https://blog.jquery.com/2019/04/10/jquery-3-4-0-released/)
and they'll be removed in jQuery 4.0.0. This PR removes their usage.
Most of the changes were possible without changing public API. However,
dropping `:even` usage required a change to the
[`header` option](https://api.jqueryui.com/accordion/#option-header)
of the accordion widget. I made it an optional function; this will need
to be documented.
The polyfill for `.even()` & `.odd()` is added for jQuery <3.5.0. There was
no usage of the :odd selector in the code but the `.odd()` method is also
polyfilled for completeness.
Closes gh-1904
Adds a data-composite option and fixes paths for effects. Otherwise
just applies the same conversion as already applied to demos, sometimes
moving a <style> element to the right place.
This adds a compound test page for draggable+resizable, which had no coverage
before. Using that page shows that there is no way to reproduce the behaviour
described in the original ticket that caused this workaround, since its not
possible to resize an element beyond the window boundaries. Therefore removing
the workaround, which is 6+ years old and has no test coverage, seems like the
sanest approach.
Fixes#6939
Closes gh-1210
