[SeaBIOS] [PATCH] Ctrl-Break support (INT 1B, etc)

[Nikolay Nikolov]

Hi, all,

I made a patch for proper Ctrl-Break handling. This is useful for MS-DOS 
or compatible operating systems like FreeDOS.

When Ctrl-Break is detected, it clears the keyboard buffer, sets the 
Ctrl-Break flag at [0040h:0071h], invokes int 1Bh and then adds 0000h to 
the keyboard buffer. If a non-enhanced keyboard is present, Ctrl-Scroll 
Lock works just like Ctrl-Break. This seems to be the "standard" BIOS 
behaviour, at least on the PCs I tested.

The patch was tested with MS-DOS 6.22, running under qemu.

I'm new to git (and this is my first SeaBIOS patch ever), so I'm not 
sure what's the preferred way to submit patches. I just did a "git diff" 
and attached the result. Sorry if that's not the best way :)

Nikolay