Code review comment for lp://staging/~robertcarr/mir/disable-sequences-and-add-terminate-handler

> This change is going to affect all shells, not just the demo shell.
> It might be worth putting alt+ctrl+backspace into libmirserver by default
> (at least for now) so other shells also are quittable if we disable input.

+1, we can put it in run_mir.cpp

> Finally, check with Alexandros but I think there was some issues that meant
> he hadn't enabled raw input yet.

My only concern is that we would disable VT switching key sequences, while we didn't yet have another way to handle them. It seems that the current raw mode options don't affect this, so no problem there.

Plus, I think that the input stack has matured enough to support this (i.e. catching ctrl-alt-f1 and initiating a VT switch), and when we get this we can completely disable VT input (something like ioctl(fd, KDSKBMODE, K_OFF), but I need to experiment), which means that we won't need FOPS::make_raw()/VT::disable_control_sequences() any more, we will just need VT::disable_input().

137 +void mgg::LinuxVirtualTerminal::disable_control_sequences()

We also need to restore the VT input handling state in the LinuxVirtualTerminal destructor, to get back to a sane console after shutdown.