Calling close when process is still alive

[Aidan63]

One I found while going over some libuv docs, you shouldn't call uv_close on a process before its exit callback has arrived, doing this doesn't result in an error but leaves the process in some sort of weird state... (libuv/libuv#1911)
While I'm sure there are good reasons why they implemented things that way it is thorougly unintuative and seems like an accident waiting to happen.
I think it would make sense if we say that calling close on a process still alive will kill it. So we'd need to some some tracking so on a close call we'd see if we need to issue kill the process and wait for its exit before doing cleanup and invoking the provided callback.