Interface to signal running state to parent process

[turbio]

Right now we're grepping for the prompt to determine running state. This is kinda janky, but has the advantage of synchronizing the state in lock stop (i.e. output and state can't race).

It'd be nice if prybar could signal out of band to the parent process when it transitions into a new state. It's important that this signal be synchronous as it is now.