Issue #5312

The hint logic of the `fromList` command did not respect the cursor position inside the token.
Now it will list all matching completions for the substring up to the cursor, instead of only the ones matching the complete token. The behavior is now the same as for the regular autocompletion.

Closes #5290

Closes #5316

When using the editor in "application/json" mode, the standard javascript autocompletion would show up once triggered. Although it's deactivated by default and doesn't make sense to enable autocompletion in JSON mode on its own, this change fixes incorrect completions once you combine the default completion with your own custom logic.

Primary motivation was to remove the use of `innerHTML` because the
Firefox extension validator raises a warning about this.

The obvious solution is to use `textContent` instead of `innerHTML`
but I thought it could be useful to have the ability to pick a
custom visual for the scroll-lock icon.

As per MDN documentation, all the supported browsers as per
CodeMirror documentation support `:after`.

Fix for mouse events that get sent to the wrong document when the script is being run in a different frame than the editor. 

Issue  #5287

Closes #5275

Issue #5265

This explicitly adds keywords that are already syntax-highlighted
and correctly parsed by CodeMirror already in the JavaScript mode.

- highlight strings
- highlight ports as numbers in expose instruction
- highlight comments as such only when they appear at the start of a line
- consider also ` as a line continuation

Turn it off for mssql

Closes #5229

[asynchronous
iteration](http://2ality.com/2016/10/asynchronous-iteration.html) is a
stage 4 ("finished") feature in ES2018, and its additional syntax - for
await loops - don't require too much change in CodeMirror's JavaScript
mode for support.

[javascript-lint] JSHINT backward compatibility - Setting error severity to error by default when there is no error.code property (#5260)

Closes #5256

CodeMirror C and C++ currently highlight the string "null", which isn't defined in C/C++. Those languages do macro "NULL", though.

Closes #5248

add more instructions
highlight instructions as 'keyword'
highlight 'from ... as'
add tests

Closes #5238