Closes #3998

Closes #3994

* \x1a-\x1f were missing though it looks like the intention was to cover all below \x20 (space)
* added \x7f which is usually considered non-printable
* removed \t which was already covered in \x00-\x19 as \x09

Issue #3979

Issue #4001

Use it to make the C++ mode not indent template statements

Closes #4001

according to Clojure's changelog: https://github.com/clojure/clojure/blob/master/changes.md

Issue #3991

Closes #3981

See https://discuss.codemirror.net/t/drag-drop-modifiers/721

"commend addon" should be "comment addon".

Issue #3976

Update from 5.13.2 to 5.14.0.

Fix "Uncaught TypeError: Cannot read property 'severity' of undefined"

Closes #3958

Issue #3973

@ as __matmul__ operator only on Python 3,

Add tests for Python mode for this use case.

Closes #3957

Issue #3974

Even if we don't use promise internally, check for the existence of
`.then` attributes on the return results of a hinting function, and if
so assume it is a promise.

Internally also convert all hinters to use the asynchronous interface
for consistency and simplification of code paths.

Closes #3971

`u` prefix are valid (again) since 3.3, and `f` prefix are now allowed
starting at 3.6 (which is not released yet though).

Closes #3972