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
Summary of the changes:
* Build: Add jQuery 3.2.0-3.4.1 to versions UI can be tested against
* Build: Load jQuery & Migrate via HTTPS
* Build: Add package-lock.json to .gitignore
* Build: Update jQuery Migrate from 3.0.0 to 3.1.0
* Build: Allow to run tests against jQuery 3.x-git
* Build: Fix formatting according to JSCS rules
* Build: Disable JSCS for the inlined jQuery Color
* All: Switch from $.isArray to Array.isArray (jQuery.isArray will be
removed in jQuery 4.0)
* All: Switch from `$.isFunction( x )` to `typeof x === "function"`
(jQuery.isFunction will be removed in jQuery 4.0)
* All: Inline jQuery.isWindow as it'll be removed in jQuery 4.0
* Effects: Fix a timing issue in a variable declaration. Previously,
a jQuery object was created, chained & assigned to a variable that
was then accessed in a callback used inside of this chained
definition. Due to a timing difference in when the callback fired for
the first time in latest jQuery master, it was being called before
the variable was defined.
* Tests: Make dialog & draggable unit tests less strict (newest jQuery
returns fractional results in some cases, making comparisons fail when
there's a tiny difference)
* All: Migrate from $.trim to bare String.prototype.trim (jQuery.trim
will be deprecated in jQuery 3.5)
Closes gh-1901
