re-imported job/signal code from old implementation

src/libsh/sys.rs

@@ -0,0 +1,18 @@
+use crate::{prelude::*, state::write_jobs};
+
+pub fn sh_quit(code: i32) -> ! {
+	write_jobs(|j| {
+		for job in j.jobs_mut().iter_mut().flatten() {
+			job.killpg(Signal::SIGTERM).ok();
+		}
+	});
+	if let Some(termios) = crate::get_saved_termios() {
+		termios::tcsetattr(std::io::stdin(), termios::SetArg::TCSANOW, &termios).unwrap();
+	}
+	if code == 0 {
+		eprintln!("exit");
+	} else {
+		eprintln!("exit {code}");
+	}
+	exit(code);
+}