Enable ^C (and incidentally ^S/^Q) in ddb.

[rang_acm.org]

Summary

I usually set $lines to 0 so that I can do large memory/buffer/etc. dumps from ddb; but sometimes it is useful to be able to interrupt the output, especially when using a relatively slow serial connection. Code for this was already present, but not hooked up for some reason. This just hooks it up to the console subsystem.

I did minimal testing, just using DDB on an AMD64 kernel, but it seems to work as expected. It's a little messy since you get the kdb reentry stack after ^C, but works.

[markj]

Nice, I've wanted this too.

The backtrace spam is a feature of many seemingly reasonable DDB actions (e.g. "show proc <pid>" when no process with that PID exists).

[jhb]

How odd that this was never hooked up.