Issue #2557

Closes #2539

Issue #2529

Added `combineTokens` for overlays that can override default
`combine` argument.

So that the click doesn't kill editor focus.

Closes #2505

Issue #2502

Issue #2475

Closes #2482

Issue #2442

Issue #2438

Issue #2439

Issue #2438

Issue #2385

It assumed it saw all parts of the stream, and started
doing bad things when that was not the case.

Issue #2410

Issue #2406

Issue #2385

Summary: If `options.async` is enabled, it's possible for `activity` to
be called a second time before the first call's paired `finishUpdate` is
triggered. Then, when the second call to `finishUpdate` happens, the
still-active widget in `completion.widget` is unceremoneously
overwritten and can now never be closed. This leads to a lot of weird
and broken behavior, notably an autocomplete window in the browser that
never goes away and can insert its text over and over and over.

Test Plan: This is really hard to trigger. My project consists of a
webworker providing autocomplete, which has some latency before it calls
the `finishUpdate` callback. But it depends on the exact latency and
even the user's typing speed to whether things happen in just the right
order. I basically just added and deleted characters with the
autocomplete prompt open a bunch until it eventually reproduced. After
applying this patch, several minutes of bashing didn't trigger the issue
again.

Closes #2376

Add tests. Adjust addons that depended on previous token structure.

Also improve indentation around implicit end tags in HTML.

Issue #2176
Issue #2333

Issue #2334

It was broken and confused.

Make the mode register a list of completable words instead.

Issue #2324

Since it's what you want most of the time, and easy to forget.

Issue #2323