Closes #3847

Closes #3846

 * Support nested block comments.
 * Improve number and operator parsing.
 * Improve string parsing.
 * Style brackets correctly.
 * Improve #-words.

Fixes #3842.

Closes #3840

It's already listed above as "MariaDB SQL".

Also add the ".mps" extension to the MUMPS mode.

Closes #3834

Issue #3821

Rather than hard-coding the bare XML mode.

Issue #3829

`serializeable` → `serializable`
Replace `an` with `a` 
Remove extra `command`

See https://discuss.codemirror.net/t/any-way-to-override-syntax-error-highlighting-in-asp-net-like-code/642

Closes #3808

This patch enables styling of active line numbers by
adding a `CodeMirror-activeline-gutter` class to the
line's gutter space.

Issue #3794

Closes #3806

Closes #3802

Closes #3800

Closes #3804

Closes #3797
Closes #3794

Closes #3803

It doesn't work inside of a transformed container, even for zero
transforms (which some components seem to love putting on root
elements, for whichever reason)

Closes #3238

Closes #3791

Issue #3790