Closes #5333

Closes #5332

Closes #5325

Issue  #5287

Closes #5275

- 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.

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

In my experience, `.tex` is a much more common extension for LaTeX documents.

Closes #5219

Closes #5197

Closes #5187

Closes #5180
Closes #5181

Closes #5178

 * Add common keywords for ML languages
 * Add builtins for OCaml and F#
 * Add Standard ML as ML language

The CREATE DATABASE command supports LC_CTYPE and LC_COLLATE keywords as
per https://www.postgresql.org/docs/10/static/sql-createdatabase.html.
This commit adds them to the postgres sql mode.