Pause execution and return to CLI on ^C

Consider this a feature request with a prototype, I guess, because I get the following when I actually try to use this:

```
dlv> continue
new thread spawned 12773
new thread spawned 12774
^CStopped at: :269
Command failed: open : no such file or directory
dlv> 
```

Is this just what happens when it stops in the runtime guts rather than go-land?