Identifiers that contain the identifierQuote like a table named
my"table are now doublicated correctly (e.g. quoting produces:
"my""table"). This fixes 2 failing tests, but 2 others still fail.

Closes #4623

Closes #4621

The identifier-quote that a language uses around identifiers can now
be defined using "identifierQuote" when defining a mimetype.
Previously, backticks where hardcoded, but this is not standard SQL
(which uses double quotes). For example, SQLite defines double quotes
as preferred way to quote identifiers:
http://sqlite.org/lang_keywords.html

Issue #4618

This reverts commit a44e76a0.

Issue #4606

https://vi.stackexchange.com/questions/6061

... in a 3-editor view, by immediately syncing the scrolling from the
left to the right and vice-versa.

As per http://spec.commonmark.org/0.27/#html-blocks

Issue #4611

Issue #4603

Issue #4603

Issue #4607

Issue #4608

So that line widgets aren't included in the background style

Closes #4606

Closes #4605

Closes #4587

js-yaml doesn't always provide line/mark data for certain exceptions;
handle this scenario more gracefully

Closes #4600

Closes #4599

Issue #4575

Closes #4595

This reverts commit 81b7760c.

Issue #4575