always use the Child to wait?

[oconnor663]

Right now we call waitpid on the side, but we could instead wait with the child itself, once waitid has returned. We'd lose the "try_wait must return Some" sanity check, but we'd gain the ability to return the child back to a caller if we want to.

[oconnor663]

And of course this will be easier after try_wait lands in libstd (rust-lang/rust#38903). But we can do it now.

[oconnor663]

An as_mut_ref method wouldn't be safe, because the caller could use that to wait (or swap out the child completely) and we wouldn't know it. But as_ref and into would be ok I think? Would they be useful?

[oconnor663]

But of course, as_ref isn't possible, because the child is in a Mutex.

[oconnor663]

Done in 0.3.0.