Signals SIGTSTP / SIGCONT not properly handled

[gwenn]

To reproduce:

1. cargo run --example minimal
2. from an other shell killall -TSTP minimal
3. from the original shell, fg

At step 3, we expect the prompt to be redrawn but nothing happen.

[gwenn]

To avoid duplicating code, we should reuse the same handler / pipe for all signals.
Like fish-shell
and mortal.
But signal-hook prevents it...

[gwenn]

I've tried to handle SIGTSTP signal but that didn't work.
I've also tried to handle SIGCONT signal without success.

[gwenn]

For SIGTSTP, maybe try to call the previous handler after restoring the original mode like isocline ?