Add modem status functionality to UART class

[cognitivegears]

This PR adds modem status functionality to UART.js. A couple of use cases for this:

1. Running a retro BBS system or BBS door game within a browser or node.js
2. Running old DOS modem terminal programs - part of what is needed for Issue DOS dialup terminal to websocket gateway #138

...or anything else that uses the UART that expects flags such as carrier detect, etc to be set.

[copy]

Thanks!

Running a retro BBS system or BBS door game within a browser or node.js

That sounds pretty cool, is this something you've been working on?

The code looks good, I've left two small suggestions. Before merging, could you do a quick pass to make sure the style is the same as adjacent code (i.e. indentation, newline between ) and {?

[cognitivegears]

Thanks!

Running a retro BBS system or BBS door game within a browser or node.js

That sounds pretty cool, is this something you've been working on?

It is :) I'm a contributor to Enigma 1/2 BBS - https://github.com/NuSkooler/enigma-bbs which is a BBS written in node.js. One of the toughest things to do with it is setting up BBS Door games. It has to shell out to an emulator. So instead, I'd like to use v86 to run the BBS DOS door game directly.

This requires a change like this though, because most Door games check the carrier detect to see if someone has hung up.

The code looks good, I've left two small suggestions. Before merging, could you do a quick pass to make sure the style is the same as adjacent code (i.e. indentation, newline between ) and {?

Will do, I ended up a little busy with work this week but should be able to finish this off this weekend. More to come.

[copy]

It is :) I'm a contributor to Enigma 1/2 BBS - https://github.com/NuSkooler/enigma-bbs which is a BBS written in node.js. One of the toughest things to do with it is setting up BBS Door games. It has to shell out to an emulator. So instead, I'd like to use v86 to run the BBS DOS door game directly.

That's very cool :-)

Thanks for the contribution, merged!